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Full text of "Chemical atlas, or, The chemistry of familiar objects : exhibiting the general principles of the science in a series of beautifully colored diagrams, and accompanied by explanatory essays, embracing the latest views of the subjects illustrated ; designed for the use of students and pupils in all schools where chemistry is taught"

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The following expressions of opinion concerning the plan of illustrating Chemistry adopted in the 
present volume, are from the most eminent teachers and scientific men in the country. It will be seen 
that the testimonials refer to the Author's "Chemical Chart ; " hut as the "Atlas" is a reproduction 
and improvement of that mode of exhibiting chemical facts and phenomena, the commendations apply 
to this work with much greater force. 


from Benjamin Silliman, LL. D., Professor of Chemistry in Yale 

I have hastily examined Mr. Youmans' new Chemical Dia- 
grams, or Chart of chemical combinations by the union of the 
elements in atomic proportions. The design appears to be an 
excellerit one. It conveys to learners the idea of chemical com- 
binations by connecting the elements by right lines with the 
compounds which they produce. Colored squares, differently 
colored in the different cases, are employed to represent the 
elements, and proportion in area indicates their relative com- 
bining weight. * * * * * * 

From "W. F. Hopkins, Professor of Natural and Experimental 
Philosophy in the U. 8. Naval Academy, Annapolis, Md. 

Having given to the Chemical Chart of Mr. E. L. Youmans 
such an examination as my small leisure permitted, I cheerfully 
state my conviction that its plan is admirably adapted to assist 
the teacher in communicating, and the learner in receiving, cor- 
rect notions of the laws of chemical combination. 

I commend it to the patronage of schools and academies 
where ehemistry is taught, and shall immediately introduce it 
into the institution with which I am connected. 

From Dr. John "W. Draper, Professor of Chemistry in the Uni- 
versity of New York. 
Mr. Youmans' Chart seems to me well adapted to communi- 
cate to beginners a knowledge of the definite combinations of 
chemical substances, and as preliminary to the use of symbols, 
to aid them very much in recollecting the examples it contains. 
It deserves to be introduced into the schools. 

From James B. Rogers, Professor of Chemistry in the University 
of Pennsylvania. 
We cordially subscribe to the opinion of Professor Draper 
concerning the value to beginners of Mr. Youmans' Chemical 

Professor of Chemistry in the College of Physicians 
and Surgeons, New York. 

Late Professor of Chemistry in Columbia College, S. C. 

From James R. Chilton, M. D., Chemist. 
I have examined the Chemical Chart of Mr. E. L. Youmans, 
and am much pleased to say that it is a valuable means of read- 
ily imparting a correct knowledge of the nature of chemical 
combinations. A variet} 7 of compounds are dissected so as to 
show at a glance their ultimate atomic constitution, in such a 
way as to impress it more forcibly upon the mind than could be 
effected by any other method with which I am acquainted. To 
those who are studying to obtain a knowledge of elementary 
and agricultural chemistry, as well as to all learners of chemical 
science, Mr. Youmans' Chart will render easily understood what 
might otherwise appear very difficult. 

From Dr. Thomas Antisell, Professor of Chemistry in the Ver- 
mont Medical College. 
Experience in teaching theoretical and practical chemistry 
for many years, has convinced me of the great benefit derivable 
from exhibiting the chemical elements in a material form to the 
eye, and I therefore take great pleasure in bearing testimony to 
the utility and value of Mr. Youmans' Chart. It represents the 
orincipal elements, binary compounds and salts, those minerals 

which interest chiefly the geologist and agriculturist, together 
with the most important organic bodies. It is got up in a style 
which renders it a neat appendage to the lecture-room, and 
wherever chemistry is taught in schools and public institutions, 
it will be found an invaluable assistant to both teacher 
pupil. * ***** 



From Prof. Gray, Author of Text-Books on Natural Philosophy 

and Chemistry. 

Mr. Youmans' Chart presents to the eye a clearer view of the 
manner in which the atoms of chemical compounds are united, 
than could be gained by the most labored description. * * * 

It would be especially useful to institutions not furnished 
with chemical apparatus. 

From Robert Hare, M. D., Emeritus Prof of Chemistry in the 
University of Penn., and Associate of the Smithsonian Institute. 
I concur in thinking favorably of Mr. Youmans' Chemical 
Chart. The design is excellent, and as far as I have had time to 
examine the execution, I entertain the impression that it is well 

From Alonzo Potter, LL. D., Philadelphia. 
The conception embodied in Mr. Youmans' Chemical Chart 
strikes me as a very happy and useful one, and the execution is 
evidently the fruit of much care and skill. I should think its 
introduction into schools, in connectioa with the study of the first 
principles of chemistry, was much to be desired. 

From the Hon. Horace Mann, President of Antioch College. 
I have been highly delighted by inspecting a Chart, shown 
to me by Mr. E. L. Youmans, of New York, the object of which 
is to represent the ratios in which chemical atoms are combined 
to form compound bodies. The different atoms are represented 
by square diagrams of different colors ; and then the compounds 
exhibit the exact number, or numbers, of the respective atoms 
that unite to form them, each atom retaining its original color. 
Thus the eye of the learner aids his memory ; and as the eye, in 
regard to all objects having form and color, can learn a hundred 
things by inspection, while the ear is learning one by descrip- 
tion ; so, when material objects, too minute to be seen, or too inti- 
mately combined to be distinguished, can be represented by form 
and color, the same great advantage is obtained. The power of 
the learner is multiplied, simply by an exhibition of the object, 
or its representative, to a superior sense. 

I think Mr. Youmans is entitled to great credit for the prepa- 
ration of his Chart, because its use will not only facilitate acqui- 
sition, but, what is of far greater importance, will increase the 
exactness and precision of the student's elementary ideas. 

From George B. Emerson, Esq., of Boston. 
I have had the satisfaction of examining the Chemical Chart 
prepared by Mr. Youmans, and very gladly give my testimony 
to its value. The author avails himself of color to represent 
properties, and of magnitude to indicate quantities; and by a 
judicious selection and skilful use of these representatives, he 
makes remarkably clear to the eye, and very easily remembered, 
the mo.-t important principles and laws of the science, and ren- 
ders intelligible many of the changes in chemical substances 
which are of most frequent occurrence and of the greatest in- 
terest. I would strongly recommend the use of the Chart to all 
teachers of chemistry. 

Fr ■' Sam'l S. Randall, Superintendent of Schools of the City of 
Ncn< Y<>rL\ a ml Editor of District School Journal of Education. 
I have examined Youmans' new Chart of Chemistry, designed 
to present to the eye of the student of this science the funda- 
mental principles of chemistry, and the ratios in which the va- 
rious chemical atoms are combined inthe formation of compound 
bodies ; and.cheerfn.Uy recommend it to the attentiou and patron- 
age of teachers, trustees* and directors of public schools, as well 
adapied to promote a knowledge of the beautiful science for the 
il ustration of which it is designed. 

From Joseph McKeen, Deputy Superintendent of Common Schools 
■in New York City. 
I have been greatly pleased with an examination of a Chart 
of elementary chemistry, by Mr. Youmans. It seems to me that 
it so simplifies the subject, that pupils in the best classes in our 
common schools may acquire from a few lessons, with its aid, 
more knowledge of the laws and principles of this science than 

I from months of study without such means of illustration, I know 
of no other chart like this; and as by its means chemistry may 

I now be taught with the same facility as geography or astronomy, 
I would earnestly commend it to the attention of school-commit- 

| tees, teachers, and learners. 

In the above view of the utility of Mr. Youmans' Chemical 
Chart, I fully coincide. 

Superintendent of Schools, Brooklyn, L. 1. 

" P 

From the Boston Common School Journal. 

We consider this Chart a great simplification of a somewhat 
confused subject; and we welcome it as another successful at- 
tempt, not only to simplify truth, but to fix it in the mind by the 
assistance of the eye. If we were called to teach the elements 
of chemistry in a school-room, we should be very unwilling to 
lose the valuable assistance of this ingenious chart. 


From Prof. War. H. Bigelow, Principal of Clinton st. Academy. 

I have introduced Mr. Youmans' Chart and Class-Buok into 
the institution under my charge, and am very happy to say, 
after subjecting them to a practical test, that they are better 
calculated to excite the interest and fix the attention of pupls, 
than any other works upon the subject which I have seen. 

The eminently practical character of the Ciass-Book, treat 
ing of the familiar applications of the science, is in my opinion 
its chief excellence, and gives it a value far superior to any other 
work now before the public. 

From Prof. Syme. 

Me. Youmans : Dear Sir, — I have carefully examined your 
Class-Book on Chemistry, and, in is better adapted 
for u~e iii schools and academies than any other work on the sub- 
ject that has fallen under my observation. 

The science of chemistry is highly interesting; and it would 
be difficult to exaggerate the advantages which would result to 
the community were it systematically taught in our schools. 
There is no situation in life in which a knowledge of the nature 
and properties of the elements of matter, and the laws and pow- 
ers which affect their mutual actions and combinations, may not 
prove of the greatest practical utility. The application of chem- 
ical agents in the various departments of art has been exceedingly 
serviceable ; and every attempt to popularize the study should 
be encouraged. 

Hoping that your efforts to diffuse the knowledge of chemistry 
will be duly appreciated by the friends of education, 
I remain, Dear Sir, 

Yours truly, 

Formerly Principal of the Mathematical Depart- 
ment and Lecturer in Natural Philosophy, Chem- 
istry, and Physiology, in Columbia College, and 
now Principal of P. S. No. 7. 

I cheerfully concur in the above recommendation of Mr. Syme. 

G. H. STEBBINS, P. S. No. 12. 

We entirely concur in the foregoing recommendation. 
F. D. CLARKE, Prin. of P. S. No. 3. 
S. C. BARNES, Prin. of P. S. No. 4. 
CIIA'S McGREGOR, Prin. of P. S. No. 2. 
W. C. ROGERS, Prin. of P. S. No. 9. 
LYMAN E WHITE, Prin. of P. S. No. 1. 
JNO. T. CONKLING, Prin. of P. S. No. 5. 
GEO. W. FITCH, Prin. of P. S. No. 6. 
CIIA'S H. OLIVER, Prin. of P. S. No. 11. 
JOSIAH REEVE, Prin. of P. S. No. 8. 
A. B. CLARKE, Prin. of P. S. No. 13. 

From Prof. J. Mulligan, Principal of Young Ladies' School, 

New York. 
I have read a Considerable portion of Youmans' Class-Book of 
Chemistry. I think the author has presented his subject in a 

more attractive aspect than it has been presented in any of the 
manuals in common use. His terse, lively style, and his continual 
reference to the important practical applications of chemistry, are 
well calculated to interest the learner. 

We have a large number of school-books for the purpose of 
giving elementary instruction in chemistry — possessing various 
kinds and various degrees of merit; but of all which I have ex- 
amined, I should prefer the Class-Book of Chemistry, as the most 
perspicuous in style and in method, and as containing the happiest 
selection of what is most interesting, and most practically valua- 
ble in the vast field of chemical science. 

From the N. Y. Commercial Advertiser. 

Either for schools or for general reading, we know of no ele- 
mentary work on chemistry which in every respect pleases us so 
much as this. 

From the N. Y. Tribune. 

We have rarely met with an elementaiy scientific treatise 
which in clearness, brevity, and freedom from extraneous matter, 
surpasses the present volume. 

From the Albion. 

A remarkably interesting and thoroughly popular work on 
chemistry, recommended to the general reader by the clearness 
of its style and its freedom from technicalities. 

From the National Intclliejencer. 

Besides the fulness with which this work treats of the chem- 
istry of agriculture and the arts, we regard it as chiefly valuable 
for the clear account it gives of the action of chemical agents 
upon the greatly varied functions of life. It is very elementary 
and practical ; and whether for the use of schools or of private 
libraries, it is an appropriate, because an instructive and enter- 
taining book. 

From the Scientific American. 

Such a book, in the present state of chemical science, was de- 
manded ; but to present the subject in such a clear, comprehen- 
sive manner, in a work of the size before us, is more than we ex- 
pected. The author has happily succeeded in clothing his ideas 
in plain language — true eloquence' — so as to render the subject 
both interesting and easily comprehended. The number of men 
who can write on science, and write clearly, is small ; but our 
author is among that number. 

From the Farmer and Mechanic. 

A Class-Book of Chemistry for the use of beginners and 
young student", which should be divested as much as possible ol 
its tedious technicalities and dry repulsiveness, so often attending 
their first efforts in this important study, has long been a desider- 
atum. To supply this need, the present volume is fully adequate. 
It is designed as a popular introduction to the study of this beau- 
tiful science, and presents it in such a manner as to win the at- 
tention and engage the interest. 


■ "* '' ''&*** ^sJds.&tO 











Wherever it is vouchsafed to the feeble senses of man to cast a glance into the depths of creation, he is compelled to acknowledge the greatness and 
wisdom of the Creator of the world. The greatest miracle which he is capable of comprehending is that of the infinite simplicity of the means, by the 
co-operation of which order is preserved in the universe as well as in the organism, and the life and continued existence of organized beings secured. — Lif.big. 




Entered according to Act of Congress, in the year 1854, by 
in the Clerk's Office of the District Court of the United States for the Southern District of New York. 













































Every experienced teacher understands the necessity of making the acquisition of the elementary and foun* 
dation principles upon which a science rests, the first business of study. If these are thoroughly mastered, 
subsequent progress is easy and certain. The system of illustrating Chemistry, which will be found in the 
following pages, is designed to aid in effecting this object. Those portions of the science which it is 
important should be well learned, and which are also considered usually as most irksome and difficult, are 
here presented in such a manner as to be quickly perceived and long retained in the memory. Of course 
very much that belongs to chemical science does not fall within the scope of this method of illustration ; 
but the great laws of combination which constitute its basis, the composition of compound substances, 
and many chemical changes and transformations, may be so clearly and correctly exhibited in pictures to' 
the eye, as greatly to facilitate acquisition, and thus afford the student a large economy of time and labor. 
The Atlas is intended to accompany the author's Class-Book ; but it may be employed with equal con- 
venience and advantage in connection with any of the school text-books. It is to be used in exactly the 
same manner as a geographical atlas. As the pupil proceeds with the work in hand, whatever it may be, 
reference should be made to the diagrams as often as the subject may require. For example ; when com- 
bining proportions, salts, combustion, or compound-radicals are reached, the plates which illustrate these 
subjects will be resorted to for assistance by those who possess the work. The text contains not only full 
explanations of the diagrams, but it consists of a series of essays or chapters upon the subjects illustrated. 
It will be observed that the reading matter is not a repetition of what is contained in the class-books. 
Where the same topics are treated, the statements are here more full, for they present the subject in a 
new aspect ; while much of the contents of the Atlas is new information, which may be profitably superadded 
to that found in the books. For the convenience of those who may desire to use them, questions have 
been subjoined at the close of the volume, which will be found to refer to the numbered paragraphs. It is 
recommended that, as pupils advance to the various subjects in their text-books, they study carefully those 
portions of the Atlas which treat of the same points. Teachers will also find, that after going through with 
other books they may make effective use of the Atlas, in the way of review j thus fixing clearly in the mind 
the general principles of the science. 


The Atlas of Chemistry is offered as an extension of the principle embodied in the Author's large 
Chemical Chart. That chart was published four years ago, and has met with a degree of favor 
from all classes of instructors rarely accorded to a novel method of illustration, especially in the 
department of science. It has passed through several editions, and the testimonials of its service- 
ableness and value as an aid in teaching elementary chemistry, which have appeared from all 
quarters, afford a gratifying assurance that the work was not done in vain. The atlas form has 
been adopted at the solicitation of numerous persons — teachers and others — who have expressed a 
desire to possess the work in a more portable and convenient shape. Though the scale of the 
diagrams has been so reduced as to bring them within much narrower limits, yet their application 
has been greatly extended, so as to embrace a larger class of subjects, and include those views 
of the science which have been recently established, and are of most general interest. 

Of the value and importance of some such plan of illustrating Chemistry there can be no longer 
a doubt. Indeed, the surprise almost universally expressed is, that something of the kind was not 
devised and adopted long ago. The superiority of the eye over all other senses, as a means of edu- 
cation, is undeniable. The beginning of the intellectual progress of the human race consisted in 
the invention of letters and words as visible symbols of sound and thought ; and to teach those 
symbols remains still the starting point of education. So also with music : it rose to the dignity 
of a regular art only when musical notes were invented, by which it became possible to express 
harmonies of sound to the eye. The symbolism in both cases is perfectly arbitrary ; nevertheless, 
when once acquired, it becomes an instrument of wonderful intellectual power. But if the mind is 
capable of being thus greatly aided by ocular signs, when there is no natural relation between them 
and the objects they represent, how much more must its power be multiplied when the symbols it 
employs assume the pictorial character, and become in a manner actual imitations of the things to 
be considered. 

It is especially in natural science, where definite and exact ideas of properties and relations are 
to be communicated to the mind, that the employment of visible diagrams is most useful. When- 
ever the object to be contemplated cannot itself be seen, and consists of such fixed elements or 
qualities as are capable of being represented or delineated to the eye, pictorial illustrations become 
indispensable. In Mathematics, we diagramize geometrical conceptions. In order to grasp and 
hold the elements and conditions of calculation with sufficient steadiness for the mind's eye to 
contemplate them, they must be displayed before the physical eye. In Astronomy, where the 
scheme of arrangement is too complicated and extensive to admit of direct observation, pictures of 


planets and planetary systems are indispensable. In Geography, which reveals to us the figure 
of great masses of land and water, the direction of mountains and rivers, the situation and hounds 
of countries, and the position of localities — facts which we cannot acquire by immediate observance — 
maps are universally employed. In Geology, also, whether to impart ideas of the formations pre- 
dominant in various regions, or actual or ideal representations of the earth's crust, visual appliances 
are equally essential. Physiology uses drawings to teach the structure of living beings ; and even 
History avails itself of ocular methods to convey to the mind its facts of time, succession, synchron- 
ism, the progress and decline of empires, &c. In all these departments of study, and many others, 
it is established that written descriptions appealing to the imagination and conceptive faculties are 
every way inferior to visual representations, as a means of communicating knowledge. 

Now the use of diagrams is as essential in Chemistry as in any other branch of study, although 
for a different reason. In this science, instead of dealing with objects whose magnitudes and dis- 
tances place them beyond direct inspection, we encounter the very opposite difficulty : we have to 
consider matter in its minutest possible form. The chemist does not stop with matter in any of its 
perceivable aspects ; he carries his thoughts downward beyond the utmost regions of microscopical 
observation, until they rest finally upon indivisible atoms — solids of almost inconceivable minute- 
ness. These atoms are not objects of sense ; we can neither see nor touch them. They lie beyond 
the reach of the sharpest scrutiny : they are the offspring of thought — occupants of an imaginary 
world. The chemist is compelled to contemplate matter in a form of minuteness which the senses 
cannot recognize, and it therefore becomes to him an intellectual abstraction. It is precisely for 
this reason, because chemical phenomena do not fall within the sphere of the senses, and therefore 
cannot be understood by simple observation, that the science is so recent in origin and development, 
and people generally are so tardy in acquiring it. For thousands of years, it has been the constant 
business of each of the thousand millions of human beings who have successively appeared upon the 
earth, to breathe the surrounding air, and at each breath to impress upon it a vital change ; and 
yet it is almost within the memory of men still living that the nature of this change was first dis- 
covered ; and this for the obvious reason, that the alteration which the air undergoes by breathing 
is not manifest to the senses. It remains the same invisible, transparent medium after respiration 
that it was before. It is evident, therefore, that the student of Chemistry stands in quite as much 
need of ocular assistance in mastering the rudiments of his science as those who habitually employ 
it in other branches of study. Nor is there any difficulty in employing diagrams, in a systematic 
and effective way, for the illustration of Chemistry. The science not only needs it, but it is 
admirably adapted to this method of exposition. The relations of atoms, the composition and struc- 
ture of compound substances, and the numerical laws of quantity, by which chemical combination 
is always governed, may all be accurately represented to the eye, so as to convey clear and distinct 
impressions. Difference of color is employed to indicate diversity of properties among the chemical 
elements. As each element has its specific properties, which it preserves in all cases wherever it 
may be found, so it is assigned a particular color, which it retains throughout the work, and by 
which it is constantly known. Thus black, wherever it is seen, represents carbon ; red, oxygen ; 
and so all the other elements have and maintain their respective colors. Those facts and principles 
which it is most important for all to understand, are thus brought out from the vague and shadowy 
region of abstract conception, and presented in all the exactness of reality to the most impressible 
of our senses. 

That it is important to avail ourselves of all possible expedients and contrivances to awaken a 
thoughtful attention to material objects, I suppose can hardly admit of intelligent question. It is 
the destiny of man that the life-period of his being shall be passed in a world of matter. Not only 
is he born into a material universe, but he is born of it ; not only is it to be his time-residence, but 


lie is part and parcel of its fabric, created of its elements, and participating in its constitution. But 
the simple fact that man's body is composed of matter, by no means indicates the intimacy or the 
extent of his alliance with material nature, nor is it the just measure of his interest in it. The 
system of man is less a mere physical body of a certain bulk and weight, than it is a vortex of 
forces, of which matter in a rapid state of transition is but the means of manifestation. The one 
hundred and forty pounds of material substance, of which the human body may consist, is but as it 
were the focus, into which several thousand pounds of matter — solids, liquids, and gases — are 
gathered and transformed each year. So vital is the relationship which subsists between the living 
man and the world of physical nature, that he cannot cease the introduction of surrounding matter 
into Iris system, even for a few moments, except upon penalty of death. 

Nor is it provided in the arrangement of Providence, that the life of man is to depend upon his 
passive and unconscious reception of the materials necessary to its continuance, ■ On the contrary, 
these materials are to be secured only by effort ; by forecast of mind, and labor of body ; by intel 
lectual exertion, contrivance, and care ; and by physical struggle and toil. In virtue of the 
profoundest requirements of his being, man is a creature of industry. Individuals may evade its 
performance, or may misdirect and waste their power ; but this only multiplies the burden of the 
rest. The equation remains undisturbed. Each human being, in simple self-defence from the 
destructive agencies of nature, implies and requires that a certain amount of labor — an equivalent 
of work — shall be accomplished. In compliance, therefore, with the inexorable demands of our be- 
ing, we are busy among the elements of matter. We expend upon it our multiform arts and 
industries — we ply it with all kinds of force ; change its nature in countless ways ; transform it into 
innumerable shapes, and transport it in every direction. All their lives long the mass of men 
are occupied in producing mutations of matter with whatever of intelligence and skill they may 
chance to possess. 

But it is not the humble laborer alone, the earth-worker in his field, or the mechanic in his 
shop, that is chained to matter by the invincible necessities of his vocation : the cultivators of art, 
though their jmrsuit be deemed ' divine/ are appointed to a kindred experience. It is the high 
office of art to invest its ideals with material foims. It is crowned only when its thought is 
incarnated — projected into physical embodiment. The Sculptor clothes his ideal with marble from 
the quarry ; the Painter reproduces his in colors upon canvas ; the Architect realizes his in build- 
ing together the solid stones into imposing and beautiful edifices ; and the Musician embodies his 
harmonic conceptions in atmospheric pulsations. Science, too, ' Godlike ' though it be, deals con- 
tinually with matter. Astronomy is a product of the spiritual faculty of man in its loftiest mood ; 
yet what is it but an inquest into the grander relations of material objects. And so the whole circle 
of physical science consists but of explorations into the several departments of matter. 

Again, health and disease — conditions which of all others which appertain to earth most inti- 
mately concern us — are but affections of matter — states and habitudes of the physical system. The 
first blessing of life consists in the harmonious action of the bodily mechanism. Yet this mechanism 
is susceptible of a thousand forms of disorder, by which suffering is induced, and that blessing lost. 
And not only do pleasurable and painful emotions depend upon bodily conditions, but also states 
of mind, and even the very integrity of the intellectual structure. Mental moods fluctuate with 
physical conditions, and disease of the mind's organ disturbs and even overthrows the mind itself. 

Undoubtedly the grandest fact of man's existence is, that he possesses an intelligent and im- 
mortal spirit. But what are the ordinations and appointments of this nobler element of his being ? 
That a material universe shall be the sphere of its evolution and education ; that it comes into 
being as a thought-germ planted in the soil of matter ; that by an exquisite apparatus of material 
senses, it is put into connection — brought as it were into universal contact with the physical 


world ; that it grows and expands by impressions poured in from the outward universe through the 
channels of sense ; and that power is thus acquired by which the developed soul reacts upon 
external nature. 

We thus see that in numberless ways, and in all departments of activity, the mind of man is 
occupied and identified with material objects : they are the instruments of its education ; the 
ministers of its pleasures and its suffering ; the recipients of its power ; and the witnesses and 
monuments of its triumphs. These considerations should be certainly sufficient to convince us of 
the importance of making natural science a subject of earnest thought and of more general and sys- 
tematic study. The time has come when ignorance concerning matters of the most vital personal 
moment to all can no longer be excused. The human intellect has long enough sported with sem- 
blance and fiction ; it should pass to the serious contemplation of reality and truth. 

But it is only when, through the illumination of science, we rise to something like a grand and 
solemn conception of the living relation of this universe to its Creator ; when we discover that he 
has written his claims to our profoundest admiration and homage all over every object that he has 
made ; when we get a glimpse of the wonders that are perpetually woven into the tissue of being as 
he throws the shuttle of time, and feel that we are walled in on every side as by an un- 
broken congeries of miracles ; it is only when we remember that all these orders of being and 
schemes of existence are but the ' thoughts of the Almighty/ and that each new fact and principle 
of nature which we learn lets us one degree further into the counsels of Divinity, that we begin to 
feel the real power and exaltation of those incentives which should prompt us to study the works 
and ways of God as unfolded by natural science. 

I have endeavored in the following pages to exhibit the Chemistry of the more common forms 
of matter in such a bight as to attract the attention and awaken the interest of those not familiar 
with the subject. The Atlas is not a complete or systematic chemical treatise, yet a natural order 
has been observed in the arrangement of its topics. The chemical laws which govern mineral, 
inorganic, lifeless matter, are first described and illustrated. We are then led to consider the 
rocky crust of the earth, and how it becomes changed into soil, preparatory to the development 
of plants and the appearance of life. The Chemistry of vegetable growth, by which inert matter is 
subjected to the life-inciting forces, and becomes organized, next engages our attention ; and then 
the various processes by which organized compounds are restored to the mineral state. Lastly, we 
notice the forces by which this grand cycle of changes is impelled, and the present order of things 
maintained upon the earth. 




1. The material objects around us are capable of undergoing three kinds of change : 
change of place, of form, and of nature. These changes occur in certain regular ways, 
and by fixed methods, which are called laivs. It belongs to Natural Philosophy to teach 
us the laws which govern changes of place and form in material things, and to Chemistry 
the laws which control changes in their nature. When a forest tree is felled, cut in pieces, 
transported to the mill and sawn into boards, the woodman, the teamster, and the sawyer 
are occupied in producing visible changes — alterations in the mass — changes of form and 
place — mechanical changes. But if the tree be burned to ashes, in the open air, or altered 
to charcoal in a pit by a slow smothered combustion, or if it be suffered gradually to rot, 
or be injected through its pores with preservative solutions which prevent decay, in these 
cases the changes are within the wood among its invisible particles ; they alter its nature, 
and are known as chemical effects. 

2. As Chemistry therefore inquires concerning the inner qualities — the interior nature 
of objects — its first question is, Of what are these objects composed ? They exhibit an 
infinite diversity of appearances ; are they really made up of as many different kinds of 
matter? Of what consists the countless thousands of varying mineral, vegetable, and 
animal forms with which our globe is covered ? No outward scrutiny — no sagacity of 
observation will afford an answer to these inquiries. To determine this point the chemist 
must resort to experiment. He accordingly subjects all the material objects of nature to 
a process called analysis. This term is derived from two Greek words, which signify up 
or bach to its source, and to loosen ; and it means the separation of any compound thing 
into its first or primary elements. In various ways and by numerous agencies the chemist 
submits every accessible object of nature to analytical operations. Most of these objects 


are in this way separated into new substances ; and the products thus derived may often 
be still further decomposed, giving rise to new and still different kinds of matter. But 
this process cannot be carried on to an indefinite extent. The operator soon reaches a 
limit beyond which he cannot pass ; obtains bodies which resist his utmost efforts to sepa- 
rate or decompose them. These are termed elements, simple substances, or ultimate con- 
stituents. Any substance which contains more than one of these is known as a compound. 

3. In separating compound bodies into their constituents, the chemist must resort to 
the application of force. The powers or forces which he thus employs are various. Heat 
is the most common. Nearly all vegetable and animal products can be separated into 
other and different substances by the action of heat. Electricity is a powerful decom- 
poser, and often breaks the union of compounds when heat fails. Light, mechanical 
pressure, and concussion ; the forces residing in living plants and animals and denominated 
vital ; and simple contact, as when minerals are acted upon by strong acids, are all capable 
of producing decomposing effects of greater or less intensity. 

4. If, for example, we send a current of electricity through water under proper circum- 
stances, we decompose or destroy it, and at the same time get two new substances, hydro- 
gen and oxygen, of which the water was composed. But neither a current of electricity 
sent through hydrogen, nor any other known agency applied to it is sufficient to effect its 
decomposition ; and so also with the oxygen. Marble, to the eye, appears to consist of but 
one ingredient ; but if strongly heated, as marble is every day in our lime-kilns, it is decom- 
posed or analyzed into two totally unlike substances, quicklime and a gas called carbonic 
acid. Now if a current of electricity is sent through the lime, it rends it into a silver 
white metal calcium, and oxygen ; and if the carbonic acid be heated under suitable cir- 
cumstances it is resolved into charcoal and oxygen. But our analytic progress is here 
arrested. However we may ply these products with the decomposing forces, calcium, 
oxygen and charcoal remain unchanged, yielding no new elements. 

5. Chemistry thus divides all bodies into simple and compound. But as all mattei 
has not yet been exj}lored, new elements may still be discovered ; and as we can hardly 
suppose that our analytic methods have reached perfection, some of the present elements 
are liable to turn out compounds. In the past progress of the science, bodies once 
regarded as elementary have been afterward proved compound, and numerous considera- 
tions incline chemists to suspect that many now ranked as simple will yet undergo decom- 
position. Nevertheless, we are now compelled to include as elements all bodies which 
resist the severest decomposing tests which the skill of the analyst can bring to bear 
upon them. 

6. The material things about us may thus be likened to a language. We can resolve 
its literature into sentences, its sentences into words, and words again into letters ; but 
these are primal symbols, ultimate elements, and with them our analysis ceases. Thus 
iron, sulphur, carbon, contain each but one kind of matter, and may represent letters. 
But water contains two different kinds of matter ; oil, three ; crystallized common salt, 
four ; crystallized alum, five ; and pure white of egg, six ; corresponding to words of two, 
three, four, five, and six letters. 

7. The resemblance between the composition of natural objects and that of language 


may be carried still further. The literature of our language is made up of an infinite 
number of varying sentences, and these are composed of many thousands of different 
words ; but when this vast array of words is examined, they are all found to consist of 
but twenty-six letters. And so the entire alphabet of nature consists of sixty-three or 
four letters only. Chemical analysis, which has questioned and tested every material thing 
within human reach, discloses but about sixty-three ultimate elements or simple bodies. 
From this narrow range has the Almighty Architect selected the materials which compose 
our globe and all the living beings which inhabit it. From the ponderous masses of rock 
of which mountains are built, to the fleeting and ethereal atmosphere ; from the lowest and 
simplest forms of vegetable and animal life upward to the most complex and highly- 
endowed orders of living beings, whatever the diversity of their aspects, properties, 
powers, or functions, they have all been created out of this small number of elementary 

8. Again, in the structure of words, certain letters occur often, and others but com- 
paratively seldom. Thus, for example, in all words we find one or other of the vowels, 
while the letter z appears but unfrequently. So in the composition of matter certain 
elements abound while others are discovered but rarely. If it seem wonderful that the 
Creator should have formed the world and all its occupants out of sixty-three or four 
elements, how must it deepen our surprise and admiration when we learn that in carrying 
forward the grand operations of the globe, he can hardly be said to use more than one- 
fourth of these elements. By far the greatest portion of terrestrial matter, organic and 
inorganic, earth, sea, and air, with all their inhabitants, are composed of but twelve or 
fifteen elemeuts. Nor is this all ; for a single elementary substance, oxygen, composes at 
least one-half of the entire terrestrial universe. These marvellous facts give to Chemistry 
a simplicity which corresponds with its importance. In studying the composition of air 
and water, of rocks and soil, of our own bodies and the foods which nourish them, in 
short, the application of Chemistry to vegetable and animal beings, and to that parent of 
arts and noblest of occupations — agriculture, we find ourselves constantly engaged with 
the same few elements. Our attention will be restricted entirely to these in the present 

9. Yet analysis, which has conducted us to these interesting facts, is but half the busi- 
ness of the chemist. As we can separate sentences and words into letters, so we can put 
the letters together again and form words. The chemist also, when he has analyzed a 
compound, may often reunite his elements and reproduce his compound. This putting 
together of elements is the reverse of analysis, and is called synthesis. In analysis we 
pass from complexity to simplicity ; in synthesis we turn round as it were, retrace our 
steps, and go from simplicity to complexity. In the laboratory of nature, as well as in 
that of art, these operations constantly alternate and frequently proceed together. But 
in the case of language we do not merely form such words as have existed before, but 
may combine the letters so as to make new ones ; so in Chemistry we may not only repeat 
compounds which already exist, but we may create new ones. Thus glass, soap, chloro- 
form, are compounds which, so far as we know, are not found in nature, but are products 
of art. In this direction, the formation of new substances by synthesis of their elements, 


the possibilities of chemical progress are boundless. It should however be always 
remembered that we have no power of creating new elements, or essentially new matter. 
We can only produce substances with new properties out of our existing materials. 

10. When we separate these elements from the compound forms in which they most 
naturally exist, and examine them individually by the artificial methods of the laboratory, 
we are filled with amazement at the contemplation of the properties with which they are 
endowed. Apparently quiescent and inactive, they are nevertheless clothed with the 
mightiest energies. From the inert, torpid, slumberous state they suddenly pass as it were 
to conditions of wakeful irritability or the extreme of violence ; now rushing into vivid 
and intense combustion, and then furiously exploding with peril and ruin to all around. 
And yet it is these seemingly unmanageable and discordant elements that are chosen by 
the Omnipotent to carry forward the grand phenomena of life and being upon the earth. 
How simple and yet how mysterious ! How numerous the forms and how changing the 
aspects under which they appear ! How dissimilar and opposed the purposes to which 
they minister ! How wonderful their adaptive powers ! Guided by his hand, each per- 
forms tranquilly its destined office, moves through all the varying phases of decomposi- 
tion, decay, and death, then rises into new life, takes on the vital form, and passes again 
through the same round of transformations. Thus bodies which in the chemist's shop are 
looked upon as agents of terror, in the laboratory of nature become ministering spirits, 
as it were, to watch, guard, and preserve us. 

11. If the simple elements were to be placed promiscuously upon a table, a child would 
be able to divide them by their external appearance into two classes ; the one possessing 
the metallic aspect and the other without it. The first are called metals, the second 
metaloids or non-metallic elements. Three-fourths of all the known elements are metals. 
The simple substances with which we are mainly concerned are derived from both these 
classes. They are fifteen or sixteen in number, and have been called the organic or zootic 
elements, because they form all structures in which life is manifested. 

12. In Plates I. and II. the names of these elements are given in the left columns ; in 
the first the metaloids, in the second the metals. Opposite each name is placed a colored 
square, which is designed to represent the element. As each simple body has its own 
peculiar properties, so it is assigned a different color. These colors have not been selected 
at random ; they all have a meaning and are associated with facts which it is useful to 
remember. Oxygen is the great agent of combustion ; it also changes the dark or venous 
blood of the animal system to a bright red in the lungs ; it is hence properly symbolized 
by a red diagram. When water is decomposed by potassium, its hydrogen burns with 
a lilach or purplish flame ; this color is assigned to the hydrogen. Nitrogen is represented 
by a sky-blue ; it forms four-fifths of the atmosphere, which is of this color. When seen 
in small quantities the air appears transparent, but when we gaze through large masses, 
as at a mountain in the distance, or up into the clear sky, its color becomes apparent. 
Carbon, sulphur, chlorine, phosphorus, and silicon are shown of their natural colors. 
Potassium, sodium, calcium, and magnesium form compounds which have a common pro- 
perty of restoring vegetable blue colors when other substances have expelled them. This 
is their test. The intensity of the colors indicates the strength of their properties. Potash 



Elementary Substances. 


o s 
















The areas of the squares correspond to the equivalent num- 
bers, and represent to the eye proportional quantities by weight. 

Binary Compounds. 

Watek, H 

Ammonia. H 3 N 

Carbonic Oxide, C 

Carbonic Acid, C 3 

| I 
Light Carbureted Hy- 
drogen, H 2 C 

Chief products 
of the decom- 
> position of veg- 
etable and ani- 
mal substances. 

m l 1 

Sulphureted Hydro- 
gen, H S 

Nitrous Oxide, N 

Nitric Oxide, N 2 

Hyponitrous Acid, N 3 

Nitrous Acid, N 4 

Nitric Acid, N 5 

Hydrochloric Acid, H CI 

Sulphurous Acid, S 2 

Sulphuric Acid, S 3 

Phosphoric Acid, P 5 

Group il- 
the law of 





Elementary Substances. 

OXYGEN, ■ \ 

O 8 























Binary Compounds. 


Potash, K 

Soda, Na 

' Lime, Ca 

Magnesia, Mg 

Silica, (Sand,) Si 3 

Alumina, (Clay,) Al 2 O3 

Mineral Consti- 
tuents of Soils. 

Protoxide of Iron, Fe O 

1 I 

■ ■ ■ I 1 . - . i. ■ . 

> Alkalies. 


► Earths. 

Sesquioxide of Iron, Fe 2 3 


Protoxide of Manganese, 


The areas of the squares correspond to the equivalent num- 
bers, and represent to the eye proportional quantities by weight. 

Peroxide of Manganese, 
Mn 2 


is the strongest, soda next, lime is weaker, and magnesia weakest of all. Aluminum is 
the basis of clay, and is given a brownish clay color. Iron forms salts of a green, and 
manganese of a rose color. (For a description of the properties of the individual elements 
and the compounds which they form by uniting with each other, the reader is referred to 
the Class-Book of Chemistry.) . 


13. The right columns, Plates I. and II., represent compounds, and they are seen to be 
produced from the elements. Lines passing from single squares at the left and uniting at 
the right indicate combination, or that attraction which draws the elements together to 
form new substances. This peculiar kind of attraction is called affinity. We see that it 
acts only between dissimilar bodies. The force which tends to draw together distant or 
separate masses is termed gravitation ; that which binds together similar particles as those 
which compose iron or sulphur, cohesion ; that which unites unlike particles, affinity. If 
the earth consisted of but one kind of matter the two former attractions might be exerted, 
but affinity would be impossible. Chemistry implies plurality of elements, and springs 
from their differences. Did the earth consist only of mercury, for example, there could 
be no Chemistry. This substance might change its form, freezing to a solid or boiling to 
a vapor, yet it would remain mercury still, with nothing to compare with it, or act upon 
and alter it. But if sulphur were added, it would combine with the mercury and form 
a compound, a new substance, and thus Chemistry would come into existence, and its bounds 
would widen as the elements were multiplied. 

14. As to the nature or cause of affinity nothing is understood. We know it only by 
its effects, which are beyond expression wonderful. The first which may be noticed is the 
apparent destruction of the elements with which it deals, that is, the destruction of their 
properties. Were we to take fragments of iron and sulphur, and reduce them to the finest 
possible powder or dust, and then mix them, we should get a meclianical compound. To 
the naked eye the properties of the iron and sulphur would be lost ; but viewed through 
the microscope they would reappear, each particle presenting all the identical and dis- 
tinctive characters of the fragment from which it came. The attributes of this compound 
would be but the sum or average of the properties of the substances which made it up ; 
just as a watch may be said to be the mechanical result of the properties and arrangement 
of the gold, silver, copper, steel, enamel, jewels, and glass of which it is composed. Each 
element retains its individuality, and hence we are able to predict the result of mechani- 
cal combination. 

15. If now we heat the mixture of sulphur and iron and thus bring affinity into play, 
we get a result which no knowledge of these substances would have enabled us to antici- 
pate. Both disappear so that the most powerful microscope can detect traces of neither. 
A new substance is j)roduced containing both, and differing widely from each. It is a 
chemical compound. Affinity has abolished the properties of those elements, and created 
from them a substance endowed with new properties. 


16. Newness of properties, either in odor, form, color, density, taste, or other attri- 
butes, belongs to all compounds formed by chemical affinit} 7- . Thus, when black charcoal 
and yellow sulphur combine, the compound formed is colorless as water and highly 
volatile. If the yellow sulphur and bluish-white quicksilver be heated together, they 
form the bright red vermilion. Waxy phosphorus and colorless invisible oxygen unite 
to form a white body resembling snow. Nitrogen and oxygen are tasteless, separate or 
mixed; yet one of their compounds, laughing-gas, is sweet, and another, nitric acid, in- 
tensely sour ; they are both transparent, invisible, and yet they form a cherry-red com- 
pound gas. Charcoal and hydrogen are'odorless ; nevertheless, many of our choicest per- 
fumes, such as oils of roses and bergamot (Plate V.), as well as the less agreeable spirits 
of turpentine and illuminating gas, contain only these elements. The mild and scentless 
nitrogen and hydrogen give rise to one of the most odorous and pungent compounds, 
ammonia; while suffocating and poisonous chlorine, united to a silver-looking metal, 
sodium, yields common salt. Charcoal, hydrogen, and nitrogen, which singly or mixed 
are not injurious to life, yet combine to form the terrible poison, prussic acid; while char- 
coal, hydrogen, and oxygen, variously united, produce sweet sugar, poisonous oxalic acid, 
and intoxicating alcohol. 

17. Substances lose their properties, when entering into combination, more or less 
completely, accordingly as those properties more or less resemble each other. If the sub- 
stances are very similar, the compound will show its parentage ; if quite unlike, all traces 
of its derivation will be lost. Thus iron and mercury, both metals, form a compound 
whose metallic aspect immediately betrays its origin ; but who, looking at the beautiful 
paint, vermilion, would guess that it contained the fluid, silver-white metal mercury, and 
the yellow inflammable metalloid, sulphur ; or that common gypsum consisted of the caus- 
tic and burning alkali, lime, and the corrosive poisonous liquid, sulphuric acid. 

18. Analysis informs us of the composition of compound bodies, what elements they 
contain, and how much of each. But when we have examined one sample of a substance, 
and determined accurately its ingredients, how far will this knowledge carry us ? Does 
the information we get extend no further than to the specimen analyzed ? Must each 
new fragment or portion of a substance be experimented upon before its ingredients and 
their qualities can be known ? 

19. If the compound we examine contain several chemical substances, mixed as it 
were by accident or chance, as is the case with soil, mineral waters, ashes, and many arti- 
cles of commerce, our information is limited to the sample analyzed. We can infer, with 
more or less probability, the composition of the larger mass from which the specimen was 
taken ; but as the mixed ingredients may vary in proportion, any conclusion which goes 
beyond the simple results of experiment must be conjectural, and therefore uncertain. 
This fact of the variable mixture of substances, their impurities and mechanical com- 
plexities, greatly multiplies the labor of the analyst. 

20. It is the interference of Mechanics with Chemistry that here causes difficulty, for- 
bidding the operator to pass beyond the naked determinations of his experiment. But 
when we enter the field of pure Chemistry, the result of every exact analysis may be at 
once expanded into a general law ; the individual fact contains a principle which may be 


carried with certainty into universal application. Affinity, in binding together chemical 
substances, does it always in certain invariable and constant proportions. The same kind 
of substance has ever the same composition. There is often difficulty in establishing that 
composition with precision ; but the fact once determined, applies always to the same class 
of bodies. Thus, when the composition of a sample of water, or common salt, or lime, is 
once certainly determined, the knowledge applies to all water, common salt, or linie. 
There is a mathematical order in the domain of Chemistry as absolute as that which 
reigns in the realm of Astronomy. This numerical order results from a few simple laws 
by which affinity is always governed. 

21. The first law of affinity is that it unites substances in definite and constant 
pkopobtions. The relative quantities of the elements in a compound may be expressed 
by numbers, and those numbers always represent its composition. Water, for example, 
consists of 8 parts, by weight, of oxygen, united to 1 part, by weight, of hydrogen, and it 
has this exact composition the world over. We can produce it by the union of its ele- 
ments in those proportions, and no other. Potash is composed of 39 parts, by weight, of 
the metal potassium, and 8 parts of oxygen. Common salt of 35 parts chlorine, and 23 
of sodium ; and so it is with all the chemical compounds. Certain numbers, ascertained by 
experiment, express the proportions in which their elements invariably unite to form 

22. As chemical substances are thus composed mathematically, each having its un- 
changeable constitution, we may, as it were, dissect them, and represent to the eye by 
diagrams their elements and the proportions in which they combine. In Plate I. oxygen 
and hydrogen are seen to be represented by colored squares. The lines passing from 
them and meeting at the right, represent affinity ; and the relative sizes of these squares 
express the law by which affinity in this case is governed. The compound, water, consists 
of two elements, there being 8 times as much of one as of the other. These facts are 
impressed on the mind by a single glance at the diagram. 

23. The numbers, 8 connected with oxygen, and 1 with hydrogen, indicate the propor- 
tions in which these elements are seen to unite. They are therefore called combining 
proportions or combining numbers, and the size or area of their squares exactly corresponds 
to them. The oxygen square is just 8 times larger than the hydrogen square. In like 
manner it will be seen that each element has its associated number and its square of cor- 
responding size. The combining number for sulphur is 16, and hydrogen being 1, when 
these unite, the compound, as we see by the diagram (Plate I.,) contains 16 times as much 
sulphur as hydrogen. Chlorine is 35, and when it combines with hydrogen to form hy- 
drochloric acid, we see that the proportions are as 35 to 1. 

24. There are two ways in which the combining proportions of chemical substances 
can be measured ; by volume or bulk, and by weight. The laws of combination by volume 
will be explained in another jDlace. But the fundamental numbers of Chemistry, which 
form the groundwork of the science, are determinations by weight. The colored squares 
that indicate combining proportions, therefore express relative quantities by weight and 
not by volume. 

25. The combining numbers are not often whole numbers; they most frequently 


involve additional fractions. For example, the exact combining number for chlorine is 
not 35, but 35-4 (see Class-Book of Chemistry.) As whole numbers are however suffi- 
ciently accurate for general purposes, and are easiest remembered, the fractions are omitted. 

26. Oxygen, 8 parts, and hydrogen, 6 parts, combine to form carbonic oxide. Their 
squares express these quantities, as the diagrams show (Plate I.) Now, if the reader 
will glance over the various colored illustrations of chemical compounds throughout the 
work, it will be seen that the black and red squares maintain invariably their relative 
size. This could not be otherwise, for the same numerical law of definite and constant 
relative proportions follows them into all their combinations. In Plates XI. and XII. 
the squares which represent carbon, oxygen, and hydrogen, are given, for convenience, of 
one fourth their usual size. Relatively, however, they are the same ; the squares express- 
ing the same proportional numbers. 

27. How more than wonderful, how almost miraculous is this order! The elements 
of the wood we burn are associated in fixed mathematical ratios. In the violence of com- 
bustion, the bond that held them together is destroyed ; they break away, but cannot 
escape the law of numerical destiny. They rush into new unions, but the combining 
numbers are still unchanged. Hie burning candle gradually wastes away before us. Its 
matter appears to be destroyed ; but it is only changed into an invisible shape — dissolved 
in the air. These changes are beyond the reach of vision ; yet down in that invisible 
region, forces are playing among the invisible particles with the same harmony and exacti- 
tude as those which rule the planets. And so it is with all chemical mutations. In the 
gradual growth of living structures, by the incorporation of new matter ; in the digestion 
of food ; in the slow decay of vegetable and animal substances, as well as in their quick 
combustion, the transposition of elements takes place in rigorous accordance with the laws 
of quantitive proportion. 

28. Chemical substances are united by a force ; and the combining numbers are meas- 
ures of that force. If we take equal quantities of two elements, we do not find them 
possessed of equal powers of attraction. There is as much chemical energy or neutralizing 
power in 1 grain of hydrogen as in 8 grains of oxygen. 35 grains of chlorine do not 
neutralize 8 grains of oxygen 35 times more effectually than 1 grain of hydrogen does, 
but only equally well, and with the same chemical effect, namely, the neutralization of 
both elements, and the production of new compounds. 1 grain of hydrogen, 8 grains of 
oxygen, and 35 of chlorine, are therefore, chemically, equal — have equal values, or pro- 
duce equivalent effects. Viewed in this way, combining quantities have been called 
equivalent proportions, or equivalents ; and this term expresses more clearly than any 
other, that a certain weight of one body is equal to, or goes as far as a certain but dif- 
" rent weight of another body, in the production of a similar compound. 

21). The law of definite and equivalent proportions is of universal extension, and in 
this aspect it appears as the law of reciprocal proportions. When two bodies combine 
with a third, as they are each equivalents of the third body, so they are also equivalents 
of each other, and unite together in exactly the same proportions ; that is, the same num- 
ber which applied to each in uniting with a third body is retained when combining with 
each other. Thus, 1 part of hydrogen combines with 8 of oxygen, and 35 of chlorine 


combines with 8 of oxygen ; but 35 of chlorine is the very quantity that combines with 
1 of hydrogen. These numbers may be reversed ; 8 of oxygen combines with 35 of 
chlorine, and 1 of hydrogen combines with 35 of chlorine ; but 8 of oxygen is exactly the 
quantity that unites with 1 of hydrogen : or, again, 8 of oxygen combines with 1 of hydro- 
gen, and 35 of chlorine combines with 1 of hydrogen ; but 8 of oxygen is the precise 
quantity that combines with 35 of chlorine. The doctrine of reciprocal proportions 
teaches that the proportion in which any two bodies combine with each other is that in 
which they combine with every other. Take a fixed quantity of any substance that has a 
wide range of affinity — oxygen, for example — and cause it to unite with a large number 
of elements. The quantity of oxygen in each of these compounds will be the same, but 
the quantities of the other elements will be very various ; nevertheless, when these 
elements combine with each other, exactly the same quantity of each is taken. Thus, a 
single combining or equivalent number attached to an element becomes the exponent of 
its neutralizing or saturating power, in every case of its combination. 

30. Chemical decomposition thus often consists simply in the replacement or substitu- 
tion of equivalents. Potassium, when thrown upon water, decomposes it, forming potash ; 
that is, one equivalent of potassium replaces one equivalent of hydrogen in the water- 
compound. The group of metallic oxides (Plate II., right column) may be converted to 
metallic chlorides by substituting equivalents of chlorine for those of oxygen. We shall 
see more of this principle of rejDlacernent when we come to consider the structure of salts. 

31. The equivalent numbers express certain fixed relationships of effect ; they there- 
fore have a mutual dependence, and no one can be changed without a corresponding alter- 
ation of the whole series. It is immaterial, except as a question of convenience, what 
scale of numbers we employ, provided their relative values throughout the series are 
maintained inviolate. Hydrogen combines in the smallest proportion of any element ; if 
we therefore assume its equivalent to be 1, oxygen will be 8, nitrogen 14, &c; we count 
but one way, and this scale is considered best for teaching. In analysis, it is common to 
assume oxygen as 100 ; hydrogen then becomes 12.5 and nitrogen 175. These numbers 
have the same relation to each other as 1, 8, and 14. We convert the hydrogen into 
the oxygen scale by multiplying each of its numbers by 12.5. 

32. By glancing at the column of compounds (Plate I.) there will be noticed a pecu- 
liar modification of the law of equivalent and reciprocal proportions. Water, carbonic 
oxide, and sulphuretted hydrogen, furnish perfect examples of that law ; they consist of 
single equivalents of their elements. But in carbonic acid we have a double proportion 
of oxygen, and in ammonia a triple proportion of hydrogen. This mode of combination 
illustrates the law of multiple proportions. It teaches that ivhen one body combines ivith 
another quantity larger than its regular equivalent or lowest proportion, that larger 
quantity, whatever it may be, is am exact multiple of the single equivalent number. The 
compounds of oxygen and nitrogen (Plate I.) furnish a remarkably beautiful illustration 
of this law. The proportion of nitrogen is the same in all. The smallest proportion of 
oxygen is its equivalent 8 ; in the next higher compound it is 16, or twice 8 ; in the third, 
24, or three times 8 ; in the fourth, 32, or four times 8 ; in the fifth, 40. or five times 8. 

33. If a substance can combine with more than 8 parts of oxygen, the least next 


quantity it combines with is 16. It may go past 16, but in that case it cannot stop at 
any intermediate number short of 24. It need not halt at 24, however, if it can go on 
to 32, or at 32 if it can combine with 40 : or it may pass at once from 8 to 40, or to any 
other number that is an exact multiple of the original 8. In every series of compounds 
we discover the operation of the same law. All combinations of sulphur contain either 
16 parts of it, or if not, then 32, 48, or some other multiple of 16. Iron occurs in quan- 
tities of 28, 56, 84, &c. ; that is, its quantity, if above 28 parts, can always be expressed 
by a number divisible by 28 without a remainder. The numerical laws of combination 
apply to compounds as well as to elements. The equivalent or combining proportions of 
a compound body is tlie sum of the combining proportions of its elements. Thus, the 
equivalent of carbonic oxide is carbon 6, oxygen 8 = 14 ; of carbonic acid it is carbon 6, 
oxygen twice 8 = 22. The equivalent for lime is calcium 20, oxygen 8 = 28; of marble it is 
carbonic acid 22, lime 28 = 50. The number for slacked lime (hydrate of lime) is, lime 28, 
water 9 = 37. The equivalent for sugar (see Plate VII.,) is 12 equivalents of carbon, 
each 6— 72, 10 of hydrogen, each 1 = 10, and 10 of oxygen, each 8 = 80, which together 
make 162, the equivalent number for sugar. 

34. The establishment of these simple and comprehensive laws of numerical propor- 
tion, has led chemists to the invention of a symbolic language, which enables them to 
express in the shortest manner the constitution of every compound body, the replacement 
of any of its elements, and the mode in which its constituents are supposed to be arranged. 
The letters associated with the elements (Plates I. and II.) represent them, and are termed 
their symbols. They are the first letters of either the English or Latin names of the 
elements. Thus, C stands for carbon, H for hydrogen, O for oxygen, P for phosphorus ; 
but as P could not also be taken for potassium without producing confusion, K is adopted 
for the latter element, from its Latin name, halium. Sometimes by adojDting the Latin 
term we do not quite avoid this difficulty, and so a small letter is added, as Fe for ferrum 
(iron), F alone standing for fluorine ; nor could we adopt I for iron, as that is the symbol 
for iodine. Chemical conrposition is represented by combination of the symbolic letters ; 
thus, HO expresses the composition of water, CO of carbonic oxide (see Plates I. and 
II.). A symbolic letter represents not only an element, but a single equivalent of an 
element ; O represents 8, or an equivalent of oxygen ; N 14, or an equivalent of nitrogen ; 
and S 16, or an equivalent of sulphur. If therefore a compound contains more than one 
equivalent of a body, the number which it does contain is expressed by small figures ap- 
pended to the symbols ; thus, carbonic acid is C 2 ; nitric acid, N 6 ; nitrate of potash, 
K O N0 5 ; sugar, C 12 H 10 10 ; alcohol, C 4 H 6 2 , &c. 

35. The symbolical language is exceedingly simple, and affords the memory great 
assistance in retaining the facts of chemical composition. Before its introduction, the pro- 
portions of compounds were represented in parts per hundred. Thus the composition of 
water, stated according to the percentage of its elements, is 88.889 oxygen, and 11.111 
hydrogen ; but in symbolic language the same fact is expressed simply by the letters 
HO, a double amount by 2HO, a triple quantity by 3HO, and so on. 

36. It will be noticed that in the arrangement of letters in a formula which represents 
the elements in a compound, there is always a certain order. Thus water is represented 


1 > y II O, not by O H. The H occurs first, and is always located at the left. In express- 
ing the composition of metallic oxides, the metal is always placed first, or at the left, as 
K O, oxide of potassium ; F e O, oxide of iron. The same order is preserved in the ar- 
rangement of the diagrams, and there is a reason for it. When a binary compound, as 
water or potash, is decomposed by a current of electricity from a galvanic battery, certain 
elements are always liberated at the same pole of the battery. For example, the hydro- 
gen of water is always set free at the negative pole, and oxygen at the positive pole ; 
potassium and all the metals at the negative pole, and oxygen, chlorine, bromine, cyano- 
gen, or wmatever they are combined with, at the positive pole. Now it has been sup- 
posed that these elements were attracted by the poles, and, as when electricity causes 
attractiou, the bodies attracted must be in opposite electrical states, it is assumed that 
hydrogen and the metals which go to the negative pole are in the electro-positive state — 
are electro-positive, and that oxygen, chlorine, &c, which are set free at the positive pole, 
are in the electro-negative state — are electro-negative. The electro-chemical theory, as it 
is called, assumes that it is this, namely, their opposite electrical states, which causes these 
elements to combine with each other. The position of the elements of binary compounds, 
therefore, as represented in the formula or in the diagrams, corresponds to their electro- 
chemical relation ; the electro-positive element being placed first or at the left, and the 
electro-negative element being placed at the right or last. The salts (Plate III.) will be 
seen also to follow this rule, the electro-positive base being jdaced first, and the electro- 
negative acid last or at the right. According to this view, when decomposition occurs, 
electro-positive elements can only take the place of others electro-positive, and electro- 
negative elements be substituted for electro-negative. The theory is plausible, but it 
utterly fails in organic chemistry, as we shall see (173.). 

37. It has been previously stated that the fundamental laws of chemical combination 
have been determined by the process of weighing. The balance is symbolic of Chemistry. 
Says Prof. Liebig, " The great distinction between the manner of proceeding in Chemistry 
and Natural Philosophy is that the one weighs, the other measures. The natural philoso- 
pher has applied his measures to nature for many centuries ; but only for fifty years have 
we attempted to advance our philosophy by weighing. For the great discoveries of La- 
voisier he was indebted to the ' balance,' that incomparable instrument which gives per- 
manence to every observation, dispels all ambiguity, establishes truth, detects error, and 
shows us that we are in the true path." 

38. Yet there are cases in which it becomes convenient to substitute the operation of 
measuring for the more difficult one of weighing. This occurs when dealing with gases ; 
it being much more easy to measure out a certain hulk or volume of gas than it is accu- 
rately to weigh it. They combine with each other only by equivalents in weight ; hence 
it becomes important to know what amount of bulk or volume is occupied by these equiva- 
lent weights of the various gases. This mode of measurement does not apply to solids, 
unless they are capable of being converted in some way into gases or vapors ; it cannot, 
therefore, be employed upon the great mass of chemical substances. 

39. When we take equivalent quantities of the gases and ascertain the bulk they 
occupy, we do not find that the spaces they fill have the same relation to each other as 


the equivalent weights, nor are these spaces all alike ; yet a very simple relation subsists 
between the volumes they do occupy. 

40. The manner of proceeding to determine this result is as follows : The equivalent 
number of oxygen being 8, eight grains of it are taken and placed in a glass stoppered 
vessel that will exactly contain the quantity. The vessel holds precisely 8 grains of oxy- 
gen. The gas is then removed from it, and solid phosphorus introduced in its place. The 
equivalent number for phosphorus is 32 ; so we put 32 grains of it into the glass vessel. 
Heat is then applied, and the solid phosphorus converted into vapor. It is now found 
that the vapor of phosphorus exactly fills the vessel. The equivalent iveight-s of oxygen 
and phosphorus are unequal. One is 8, and the other 4 times 8, or 32 ; but when these 
equivalent quantities are brought into the same condition of vapor, they nil equal spaces. 
Their equivalent volumes are therefore equal. 

41. To express the fact that equivalent weights of these bodies give rise to equal 
volumes of vapor, we make against each an outline square of the same size, thus: 
oxygen [_]; phosphorus [_]. 

42. If now we take an equivalent of hydrogen, or 1 grain, and attempt to introduce 
it into the vessel which held equivalents of oxygen and phosphorus, we find that it will 
only receive exactly half of it, so that it would require two such vessels as contained the 
oxygen to hold the hydrogen. The equivalent volume of hydrogen is hence twice that 
of oxygen, and is thus expressed : hydrogen 

43. The equivalent of nitrogen is 14. If now we take 14 grains of nitrogen and try 
to put them into the same vessel, we find that, as in the case of hydrogen, it will only 
hold half of it. The equivalent of chlorine is 35 ; if we weigh out 35 grains of chlorine, 
of this, too, the vessel will contain but half. The equivalent volumes of nitrogen and 
chlorine are therefore the same as that of hydrogen, and are also represented thus; 

nitrogen | | ; chlorine 

44. Suppose now we desire to combine equivalent weights of hydrogen and chlorine 
gases so as to form hydrochloric acid, we take them in equivalent volumes or equal bulks. 
And if we wish to unite oxygen with hydrogen in equivalent weights, we would take one 
measure of the former to two of the latter. Thus, to form water, we fill a vessel one 
third full of oxygen and two thirds full of hydrogen, and cause them to combine by ap- 
plying a lighted match or an electric spark. 

45. When gases combine with each other, they are often condensed into less space 
than they occupied before the union ; but frequently no change of bulk occurs. In this 
case the equivalent volume, or, as it is called, the " combining measure " of the compound, 
is the same as the combining measures of its elements. Thus one equivalent of hydro- 
chloric acid gas, or 36 grains, would four times fill the vessel that contained 8 grains of 

oxygen. It is therefore thus represented : hydrochloric acid gas 

46. But when hydrogen and oxygen combine, condensation occurs. Two measures 
of hydrogen, for example, and one measure of oxygen, form only two measures of water- 
gas or steam ; watery vapor occupying only the same space which its hydrogen would fill 
if it were free. Thus oxygen [~] ; hydrogen III; steam j ~~j | . 


47. When nitrogen and hydrogen combine to form ammoniacal gas, still greater con 
densation occurs. Ammonia is formed of one equivalent of nitrogen and three of 

hydrogen, their measures being thus: nitrogen | j |, three equivalents of hydrogen 

Yet, when chemically united, they are reduced to half this space. 

the measure of ammonia being; 


48. A few of the gases occupy the same space as oxygen, more of them occupy a 
space twice as great, and a still larger number a space four times as great as that of 
oxygen. The law of combining volumes thus appears a very simple one. Yet there are 
a few instances in which the combining measure is less than that of oxygen, and others 
in which it is also greater, and in different proportions than those stated. Still, for the 
sake of convenience oxygen is adopted as unity. 

49. The spaces occupied by gases vary with variations of temperature and atmospheric 
pressure ; these conditions must therefore be taken into the account in conducting meas- 
uring operations upon that class of substances. 


50. The laws of combining proportions, which have been explained, are the naked 
'results of experiment, and are independent of all speculation. They are the expressions 

of facts, established by direct and multiplied observation, and may be verified at any 
time by accurately analyzing a few chemical compounds. 

51. But the human mind is never satisfied with a knowledge of bare facts. It seeks 
to kuow the hidden causes which lie beyond the sphere of observation and experiment. It 
requires an explanation of the phenomena — a principle that will account for the facts, and 
that is termed a theory. 

52. The fame of Sir Isaac Newton is intimately associated with the formation of a 
theory. Bodies fall to the earth, and with accelerated velocities. The planets of the 
solar system move through space and pass in curved paths round the sun at various rates 
of speed. These are facts of observation ; what is their cause ? Newton showed that 
they might be explained, and the phenomena coordinated by assuming the existence of a 
universal force, acting in a certain manner. He assigned a cause which he proved capable 
of producing these grand effects ; and this mighty conjecture, with its train of demon- 
strations, constitutes the theory of universal gravitation. 

53. Now, for that remarkable behavior of affinity by which chemical substances com- 
bine in the manner we have seen, there must be a cause. There must certainly be some 
cause which makes it impossible for bodies to combine in any other "proportions ; some" 
thing which opposes an invincible obstacle to the increase or diminution of the combining 
quantities. What is it ? This question has been answered in a clear and most admirable 
manner. What Newton did for Physical Astronomy, by developing the theory of gravi- 
tation, Dr. John Dalton has done for Chemistry, in establishing the theory of ultimate 
atoms or the atomic theory. 



54. The term atom, signifies a portion or particle of matter exceedingly small and not 
capable of being divided. What is the testimony of observation in regard to the exist- 
ence of such atoms ? Practically, there appears no limit to the division of matter. We 
meet with continual and most surprising instances df the extent to which this process may 
be carried. For example : — 

55. Gold may be beaten into leaves so thin that 282,000 of them would form a pile 
of only the height of an inch. Nevertheless such a leaf completely conceals the object 
which it is used to gild. It moreover protects such objects from the action of external 
agents as effectually as though it were plated with gold an inch thick. 

5Q. In the manufacture of embroidery, fine threads of silver gilt are employed. To 
produce these, a bar of silver weighing 180 ounces is gilt with an ounce of gold; this bar 
is then wiredrawn until it is reduced to a thread so fine that 3400 feet of it weigh less 
than an ounce. It is then flattened, by being submitted to severe pressure between 
rollers, in which process that length is increased to 4000 feet. Each foot of the flattened 
wire therefore weighs the 4000th part of an ounce. But, as in the process of wire- 
drawing and rolling, the proportion of the two metals is maintained ; the gold which 
covers the surface of the fine thread thus produced, consists only of the 180th part of its 
whole weight; therefore, the gold which covers one foot is only the 720,000th part of 
an ounce, and consequently the gold which covers an inch will be the 8,640,000th part 
of an ounce. If this inch be again divided into 100 equal parts, each part will be dis- 
tinctly visible without the aid of a microscope, and yet the gold which covers such visible 
part will be only the 864,000,000th part of an ounce. But we need not stop here. This 
portion of the wire may be viewed through a microscope which magnifies 500 times, and 
by these means, therefore, its 500th part will become visible. In this manner an ounce 
of gold may be divided into 432,000,000,000 parts, and each part will still possess all the 
characters and qualities found in the largest masses of the metal. 

57. Dr. Wollastojst obtained platinum wire so fine that 30,000 pieces, placed side by 
side in contact, would not cover more than an inch. It would take 150 pieces of this 
wire, bound together, to form a thread as thick as a filament of raw silk. Although 
platinum is among the heaviest of known bodies, a mile of this wire would not weigh 
more than a grain. Seven ounces of it would extend from New York to London. 

58. A soap-bubble, as it floats in the sun, reflects to the eye an endless variety of the 
most gorgeous tints of color. Newton showed that to each of these tints corresponds a 
certain thickness of the substance forming the bubble. Near the highest point of the 
bubble, just before it bursts, is always observed a spot which reflects no color and appears 
black. Newton showed that the thickness of the bubble at this place was the 2,500,000th 
part of an inch ! Now as the bubble at this point possesses the properties of water as 
essentially as does the Atlantic ocean, it follows that the ultimate atoms forming the water 
must have less dimensions than this thickness. 

59. An Irish girl has spun linen yarn, of which a pound was 1432 miles in length ; 
and of which, consequently, 17 lbs. 13 oz. would have girt the globe. A distinctly visible 
portion of such thread could not have weighed more than the 1-1 2 7,000,000th of a grain; 
and yet these, so far from being ultimate particles of matter, must have contained more 


than one vegetable fibre ; that fibre being itself of complex organization, and built up of 
an indefinitely great number of simpler forms of matter. 

GO. A thread of a spider's web measuring four miles will weigh little more than a 
single grain. It has been ascertained that the thread which a spider spins, and by which 
it suspends itself, is composed of about 6000 filaments. 

61. The red color of blood is due to numberless minute globules or discs floating in a 
colorless liquid (liquor sanguinis.} In the blood of man these discs are the 3500th part 
of an inch in diameter; in that of the musk-deer they measure only the 1-1 2,000th part 
of an inch. It would require 50,000 of these discs, as they exist in the human blood, to 
cover the head of a small pin; and 800,000 of those of the musk-deer to cover the same 
surface. It follows from these dimensions, that in a drop of human blood which would 
remain suspended from the point of a fine needle, there must be about 3,000,000 of discs ; 
and in a like drop of the blood of the musk-deer, there would be about 120,000,000. 

62. But the microscope has revealed still greater wonders. Each improvement in the 
instrument displays new races of animals too minute to be observed before, and of which 
it would require the heapiug together of millions upon millions to be visible to the naked 
eye. And yet each of these is composed of members as admirably suited to its mode of 
life as those of the largest species. Their motions display all the phenomena of vitality, 
sense, and instinct. Nor are their actions blind and fortuitous, but evidently governed by 
choice and directed to an end. They have their ajypetites to gratify and their dangers to 
avoid. They possess circulating systems, often highly complex, and blood with globules 
bearing to them by analogy the same proportion in size that ours do to us. And yet 
these globules themselves, organized, possessed of definite structure and complex compo- 
sition, lead us to a point where all distinct conceptions of magnitude and measurement 

63. These facts show that down to the utmost hniits of human observation and ad- 
measurement, matter continues divisible ; but they show nothing more. They cast no 
light upon what is beyond. By the strict rule of scientific inquiry, we can be certain of 
the divisibility of matter no farther than it is proved by observation. There is no war- 
rant to infer that beyond the bounds of direct investigation matter continues divisible. 
Observation has not disclosed the existence of ultimate atoms, nor has it disproved it. 
The microscope shows that within the utmost range of its powers, and even farther dowu 
in the regions of tenuity, no indivisible particles exist. But from this point onward to 
infinite divisibility, the distance is infinite, comprising a boundless range of possibility. 
Direct experience therefore affords no aid in settling the question of the existence of 
atoms ; it must be decided, if at all, by other considerations. 

64. Now the chemist has numerous and powerful reasons for believing that all matter 
is composed of atoms, that is, of exceedingly minute unchangeable particles. It has been 
objected that we cannot conceive particles so small that, if possessing weight, bulk, and 
figure, they may not be halved or divided into lesser quantities. Granting that, chemists 
yet find themselves compelled to assume that nature does ultimately limit the divisibility 

* Condensed from Kane's Chemistry and Lardner's Hand-Book of Natural Philosophy. 


of matter. It is not insisted that in an imaginary point of view, atoms are incapable of 
division, but only that in point of fact they are not for ever divided. An atom may con 
sist, if you please, of numerous small imaginary atoms ; but, physically, it is considered 
indivisible and unchangeable. 

65. We may compare these ultimate units of matter to merchandise put up in certain 
forms, which in commerce are never broken or divided. Thus many kinds of goods pass 
through the dealer's hands, sealed up in parcels, packages, bottles, caus, and boxes, and 
which the merchant never opens. In a practical commercial sense they are indivisible, 
although absolutely they are not. 

66. The constitution of matter upon the largest scale may also afford an illustration 
of the way chemists suppose it to be constituted upon the smallest scale. The celestial 
universe is composed of mighty orbs distributed into innumerable systems throughout the 
starry regions. Yet, so vast are the distances asunder at which these orbs are set, that 
they shrink to apparent points — mere luminous particles. Compared with the spaces 
through which they move, they exhibit the minuteness of atoms, and in the scheme of 
nature they are indivisible. As there exists no force capable of separating them into 
parts, or of perceptibly altering their size or form, they are in this sense indestructible 
units. The whole universe coalesces, in this view, into one immense compound, the atoms 
of which, that is, suns, planets, and satellites, are indivisible and unchangeable. 

67. All matter is thus believed to be composed of ultimate, impenetrable, and imper- 
ishable atoms, which are endowed with certain determinate properties that we can neither 
alter nor destroy. The visible objects of nature are looked upon as being formed by the 
close arrangement of these particles or molecules, as a massive edifice is constructed by 
placing together a multitude of hewn stones or moulded bricks. Being hard and impene- 
trable, these particles do not fuse or run into larger particles, as two drops of a liquid 
metal like quicksilver flow together into a larger drop ; but under the influence of various 
constraining forces, as cohesion, affinity, or electrical power, they arrange themselves side 
by side, or in groups. 

68. Assuming that matter thus consists of associated atoms, the atomic theory teaches, 
1st, that all the atoms of the same element possess exactly the same weight ; 2d, that 
atoms of different elements possess different weights ; and 3d, that the number that indi- 
cates the weight of an atom of any element is the same as the combining or equivalent 
number for that element. For the vague and misty conception of abstract proportion, 
we substitute the distinct idea of a solid, ponderable atom. Its weight, compared with 
other atoms, is its combining number. 1 is to be considered stamped upon every particle 
of hydrogen, as if the whole amount of it in the globe had been coined at the same mint 
into pieces of exactly the same value. Carbon, in like manner, is supposed to have its 
atoms stamped with 6, oxygen with 8, sulphur with 16, &c. 

69. It is a sufficient recommendation to our acceptance of the foregoing simple propo- 
sitions, that they afford a rational and most satisfactory explanation of the laws of com- 
bining proportion. Indeed, if they are once admitted, these laws follow as a necessary 
consequence. Thus, if water is formed by the combination of oxygen and hydrogen, 
atom to atom, then its composition must be definite and constant, Every specimen of 


water must yield exactly the same number of atoms of oxygen weighing 8, and of hydro- 
gen weighing 1, so that it will be found to contain l-9th of its weight of one gas, and 
8-9ths of its weight of the other ; and this must be the invariable result, whether we 
analyze grains or tons. Again, if the atoms of each elemeut possess immutable weights, 
they must in all their cornbiuations exhibit equal and reciprocal values. Replacement 
can only take place in equivalent proportion. Multiple proportions also result directly 
from the unity of atoms. As the least quantity of an element in combination can be 
increased only by the addition of whole atoms, so the number expressing the higher 
quantity must be an exact multiple of the single atomic number. No fractional quantity 
of any element or substance can be added, because the combining atom cannot be 

70. A reference to any of the accompanying diagrams of composition exhibits the 
atomic theory in its utmost simplicity. Each colored square represents an ultimate atom. 
They are seen to be grouped or aggregated together, and not mutually diffused through- 
out each other — the integrity of each being maintained. As atoms are indivisible, so 
all squares that symbolize the same element preserve an invariable size, and are never 

71. It has been lately remarked that "if the atomic theory is not true it deserves to 
be," so clearly does it account for the phenomena of chemical combination. The strength 
of the faith of modern chemists in its reality, may be well illustrated by quoting the 
language of Liebig. " Without disputing the infinite divisibility of matter, the chemist 
merely maintains the firm and immovable foundation of his science when he admits the 
existence of physical atoms as a truth entirely incontrovertible." 

72. Such advantages does the theory offer to the mind, both in the acquisition and 
retention of chemical knowledge, that it has been universally adopted. The mind seizes 
upon the conception of solid particles more readily than upon that of abstract numerical 
ratios. Hence the language of the atomic theory is in current use. We say " atom " 
rather than " proportion," and " atomic number " rather than " combining number" or 
" equivalent number." 

73. We must not confound the idea of atomic number with number of atoms. The 
number of atoms in water is 2, its atomic number is 9, and results from adding together 
the numbers which are supposed to be stamped upon each of these atoms. The same 
remark applies to equivalent number and number of equivalents. Beginners are some- 
times confused by the statement that the composition of water is 1 to 1 and also 1 to 8. 
1 to 1 refers to the number of atoms ; 1 to 8 to the comparative quantities of matter, by 
weight, in these atoms. The diagram (Plate I.) will make this perfectly clear. 

74. It is common to apply the term atom to the smallest number or group of atoms 
that can form a compound. Thus we speak of the two atoms that compose water as an 
atom of water. So also we say an atom of carbonic acid, an atom of sugar, of gluten, &c. 

75. As from the minuteness of atoms they do not admit of inspection, nothing can 
be known of their form or shape. Many suppose them to be globular, and represent 
them by circular figures. But if conjecture is to be indulged upon this point, we should 
suggest that the globular form is more characteristic of physical phenomena, as shown, 


for example, in the spherical shape of the planets ; while the phenomena of crystallization 
would seem to associate angular forms with the idea of Chemistry. When atoms of the 
utmost minuteness gather from solutions into solids, they assume the angular figure of 
crystalline structure ; and the crystals are built up in exact geometrical forms by the con- 
stant addition of atoms. May we not then almost venture to suspect that the ultimate 
atoms themselves have angular forms ? With no reference however to speculative notions, 
I have adopted the square form of symbolic diagrams as the most convenient to represent 
unity of composition, by arrangement side by side, and also exact comparative quantities 
to the eye. 


76. By the union of the elements there result two classes of compounds with widely 
different properties, termed acids and bases. In Plate I. is represented the composition 
of several of the most important acids ; in Plate II., of the most frequently-occurring 
bases. Acids are usually distinguished by sourness of taste and by the power of altering 
vegetable colors — changing blues to red ; while alkaline bases have a peculiar acrid burn- 
ing taste, and so far as vegetable colors are concerned, they undo the work of acids, 
restoring vegetable reds to blue. But these tests, although useful in ordinary cases, are 
by no means universally applicable. Some acids and bases have no taste whatever and 
exert no influence upon vegetable colors. 

77. Acids and bases have an affinity for each other, and this is their true test. Any 
substance is an acid which is capable of combining with a base, and of destroying or 
reducing its basic properties ; and any compound is a base which can combine with an 
acid, and thus neutralize or diminish its acid properties. In the union of acids and bases 
the distinctive properties of both are lost and a new compound with new properties 
results, which is known as a salt. Thus, if muriatic acid is added to soda, common salt is 
produced ; if nitric acid is added to potash, saltpetre results ; sulphuric acid added to 
lime, gives rise to a salt, sulphate of lime — gypsum ; and sulphuric acid with soda, give 
" Glauber's salt." 

78. It would thus seem that the chemical structure of salts may be a very simple 
affair. Yet the question how they are constituted, the question indeed as to what is the 
true idea of a salt — what bodies the class shall comprehend and what reject, is by no 
means easy to answer. Two views are entertained upon the subject, which have given 
rise to much and earnest controversy among chemists. In the ordinary mode of treating 
chemical topics, this question is a very difficult one to present, especially to those untrained 
in the elements of the science ; but by means of our colored illustrations the rival theories 
become at once clear, simple, and interesting even to beginners. 

79. Plate III. represents the composition of two salts, nitrate of potash and sulphate 
of iron, according to the old and long established view. They consist each of an acid 
combined with a base ; in the first example, nitric acid with potash ; in the second, sul- 
phuric acid united to oxide of iron. Each salt has been supposed to consist of a pair of 
binary compounds, and is thus represented. These elements go into combination, and 



Structure of Acids and Salts 
according to the earlier and later views. 

Examples of 

the oxygen- 
acid salts, 
(old view.) 

Nitrate of Potash. (Saltpetre.) 

Sulphate of Iron. (Copperas.) 

Chloride of 



> decom- 



Chloride of 

(Common Salt.) 

Cyanide of 

(Prussia Acid.) 

Cyanide of Potas- 

rad i- 


Hydrated Sulphuric Acid, or 
Sulphate of Water. 

Hydrated Nitric Acid, or Ni- 
trate of Water. 

Examples of 
oxygen acids, 
or of oxacids, 
(old view.) 



The same re- 
presented as 
hydracids of 

(new view.) 

Salts of Phosphoric Acid. 


Monobasic Phosphate of Water. 

Monobasic Phosphate of Soda. 

ple of 
c o m- 
pound Biba- 

Bibasic Phosphate of Water. 




Bibasic Phosphate of Water and Soda. 

Bibasic Phosphate of Soda. 



Tribasic Phosphate of Water. 

■ ^■■' 

'Super' phosphate of Lime. 



salts of potas- 
sium and iron, 
(new view.) 


' Neutral' Phosphate of Lime. 



Tribasic or 'Basic' Phosphate of Lime. 


upon analysis we recover tliem again. Other acids, phosphoric and carbonic, as well as 
nitric and sulphuric, unite with various bases and give rise to numerous salts in a similar 
way. Thus, an acid in combination with an alkali or base, was regarded as constituting 
a true salt. 

80. Furthermore, if hydrochloric acid and soda, both binary compounds, are brought 
into contact, they unite, and common salt is formed. They apparently combine as in the 
other cases, and with a like result. But here arose a difficulty. It was discovered that 
common salt is produced not by the simple combination of hydrochloric acid and soda, 
but actually by their destruction — by their decomposition and the rejection of a portion 
of their constituents. In the analysis of common salt, we find not the two binary com- 
pounds which we used to produce it, but only a half of each. Instead of consisting of 
two binary compounds, common salt is itself but a binary compound — chloride of sodium. 
Its formation, by double decomposition, is represented by the diagram (Plate III.). The 
acid and base, hydrochloric acid and soda, when brought together are seen not to unite. 
They are split and exchange elements ; two new compounds are formed, common salt and 
water. The course of the arrows shows the direction in which the elements pass. This 
is an instance of what is known as double decomposition. Common salt, in its usual form, 
contains water, called water of crystallization, and it may be driven off by heat, with- 
out destroying the salt. 

81. Now it is evident that if we adhere to the old idea of a salt, common salt, the 
very type and original of this class of compounds must be excluded from it and denied 
the saline character. Chlorine also combines with other metals, forming compounds simi- 
lar to chloride of sodium. The elements, bromine, iodine, and fluorine, behave like chlo- 
rine, producing binary compounds with the metals. These have been all ranked together, 
and, in consequence of their resemblance to sea-salt, have been designated haloid salts. 
The elements just enumerated, which unite with metals to form these salts, are termed 
halogens (salt-producers). But these haloid compounds certainly cannot be regarded as 
salts unless we modify our old conception of what a salt essentially is. 

82. The doctrine of salt-radicals is an attempt to relieve the subject of its difficulty. 
It offers us a new view of the constitution of salts, claimed to be more comprehensive and 
just. The doctrine seems to be gaining favor with leading chemists, although it is not 
yet sufficiently well established to revolutionize the nomenclature. It begins by remodel- 
ling the old idea of the structure of acids. 

83. When oxygen was discovered, and first made a subject of inquiry toward the 
close of the last century, its presence was detected in many acids. It was supposed to be 
the universal acidifying principle, and hence named oxygen (cicidsproducer^. But this 
opinion was afterward found to be erroneous. Powerful acids were discovered which 
contained no oxygen ; and so far from being peculiar to acids, this element was found 
to be even more universally a constituent of bases, and might hence, with better 
propriety, be named a base-producer. The class of acids in which oxygen exists are 
termed oxacids. 

84. Now chlorine and several other elements combine with hydrogen and form a class 
of acids in which this latter element is the common principle, and they are hence termed 


hydracids. The elements which here combine with hydrogen are called radicals; so 
H R (hydrogen and radical) represents the composition of each of the hydracids. 

85. There are two kinds of radicals. Chlorine, iodine, &c, being undecomposable 
bodies, are called simple radicals. But there are certain remarkable compound bodies 
which behave in exactly a similar way with these simple elements, and are hence called 
compound radicals. One of these is known as cyanogen ; it consists of two atoms of car- 
bon united to one of nitrogen, and comports itself, in relation to other substances, precisely 
as if it were a simple element. It combines with hydrogen (Plate III.), forming an acid, 
hydrocyanic or prussic acid, just as chlorine with hydrogen forms hydrochloric acid. The 
prussic acid, to be sure, as we see, has three elements, but it is nevertheless considered, in 
the manner of its union, as strictly a binary compound — a hydracid containing a com- 
pound radical. 

86. It has long been known that the acid properties of the oxacids, sulphuric, nitric, 
<fcc, are only developed in the presence of water. They combine with water, forming 
what are called hydrates, and it is only in this state that they become strong and active. 
The advocates of the later theory insist that, as these compounds do not take on distinct 
and decided acid properties, except by association with water, therefore they are not true 
acids, except in combination with water, in the condition of hydrates. It is objected that 
this view does not hold true of carbonic and silicic acids, which are not thus united with 
water. To this the adherents of the radical theory reply, that these compounds " possess 
very feeble and ill-marked acid properties, being incapable of neutralizing the alkalies, 
and forming with them an almost unlimited number of compounds." — Gregory. 

87. As therefore the class of hydracids all contain hydrogen, and as the oxacids do 
not manifest decided acid powers, except in union with water, which also contains hydro- 
gen — as therefore hydrogen is present in both classes of acids, it is maintained by the par- 
tisans of the new doctrine, that hydrogen, instead of oxygen, is the real acidifying 

88. The way in which water has been generally supposed to be united to the acids is 
shown in Plate III. It has been looked upon as combining in the same manner as a 
base, so that hydrated sulphuric acid appears as a sulphate of water; hydrated nitric acid 
as nitrate of water. They were considered as double binary compounds, analogous in 
structure to the salts, sulphate of iron, and nitrate of potash. 

89. Those who adopt the salt-radical view, object to this. They say we have no evi- 
dence whatever that water combines with the dry acid in this manner ; that we are under 
no necessity of regarding the hydracids and oxacids as differently constituted, forming 
two classes with but one property ; and that, as they exhibit a common character, they 
have a common structure also. 

90. The new theory therefore supposes, that the elements which unite with hydrogen 
in the oxacids exist in the form of a compound radical, and that the hydrogen is united 
directly to this radical, forming a binary compound — a true hydracid. Thus in sulphuric 
acid, the hydrogen is supposed to be united to a compound, consisting of one atom of sul- 
phur and four of oxygen, S 4 (Plate III.). This supposed compound has received the 
name of sulphion. In nitric acid, the hydrogen is believed to be united to a compound 


radical, N 6 , named nitration (pronounced nitrati-on, with a hard t, and the tion as a 
dissyllable). This brings the acids all into one class. As hydrochloric acid is a chloride 
of hydrogen, and hydrocyanic acid is a cyanide of hydrogen; so sulphuric acid is a sul- 
pMonide of hydrogen, and nitric acid a nitrationide of hydrogen. Phosphoric acid is also 
assumed to have its radical plwspliion, P 6 ; and, in the same manner, all the oxacids 
which combine with the elements of water. 

91. The advocates of the old view object that these alleged compound radicals, 
sulphion, nitration, &c, have not been isolated or separated, and cannot be proved to 
exist. To this it is replied, that compounds of this nature have been isolated, and do 
exist, in the separate condition, as cyanogen and several others. The existence of such a 
class is therefore established. Again, that chemists must and do admit the existence of 
many compounds which have not yet been set free ; — that the dry nitric acid N 5 was 
long admitted to exist, although unknown in the separate form, and has been but lately 
obtained in a free state ; and that the radicals S 4 , or N 6 , are liable to be set free at 
any time. 

92. From this point of view, the composition of salts becomes a very simple matter. 
By replacing the hydrogen of hydrochloric acid with the metal sodium, we get common 
salt (Plate III.). By replacing the hydrogen of hydrocyanic acid by the metal potas- 
sium, we produce a salt — cyanide of potassium. So by replacing the hydrogen of sulphi- 
onide of hydrogen, by iron, we have the salt sulphionide of iron, or copperas ; and by 
replacing the hydrogen of nitrationide of hydrogen by potassium, we get nitrationide of 
potassium, or saltpetre. 

93. Hence, according to Dr. Gregory (one of the latest and ablest expositors of this 
view), " an acid is the hydrogen compound of a simple or compound radical, possessing 
the power of neutralizing bases ; and its general formula is H R (hydrogen and radical)." 
Hence, also, the definition of a salt, according to the newer view, as given by Dr. Gregory : 
" A salt is the compound formed by replacing the hydrogen of an acid by a metal, and 
the general formula for a salt is M R (metal and radical). 

94. It may be noticed, that whatever view we take of the structure of an acid, if it 
contain water, it is turned into a salt by substituting a metal for its hydrogen. All the 
diagrams in Plate III. concur admirably to illustrate this fact. It will be also now 
understood why chemists incline to consider hydrogen as belonging to the class of metals, 
although in its separate state it is an invisible gas, and the lightest substance known. As 
it assumes the relationship of the metals, keeps their company, and performs their offices, 
it is thought entitled to be ranked with them. If it be light, so also is potassium, which 
floats upon water like cork ; if it be an invisible gas, so also is vaporized mercury ; and 
yet nobody doubts that these are metals. 

95. The group of compounds with phosphoric acid (Plate III.) illustrates, in a strik- 
ing and beautiful manner, the part played by water in union with oxacids, and also the 
phenomena of replacement. This acid combines with water in three proportions. An 
equivalent of acid combining with a single equivalent of water, forms the monobasic 
phosphoric acid ; an equivalent of acid to two equivalents of water, gives rise to bibasic 
phosphoric acid ; and one of the acid to three of water, produces tribasic phosphoric acid. 



Now, "by substituting alkalies or metallic bases for tlie combined water, we get three 
distinct and independent series of salts, namely, monobasic phosphates, bibasic phos- 
phates, and tribasic phosphates. The proportion of water which the acid contains, deter- 
mines the proportion of alkaline base with which it will unite. 

96. The monobasic acid gives rise to a series of monobasic salts, of which monobasic 
phosphate of soda is an example. The bibasic acid produces a series of bibasic salts, in 
which one atom of water may be expelled by an alkali and the other retained ; or two 
atoms of alkali may replace both atoms of water, as the symbols indicate (Plate III.). 
A third series of salts is formed by the tribasic phosphate of water, in which the water 
atoms may be successively replaced by one, two, or three atoms of an alkali, forming 
three different salts, as is shown by the colored illustrations. 

97. I have here selected the phosphate of lime, as being most interesting in an agri- 
cultural point of view. The phosphate of lime, as it occurs in bones, is tribasic ; that is, 
there are three atoms of lime united to one of phosphoric acid. This is distinguished as 
the basic phosphate of lime. From this salt an atom of lime may be expelled ; but an 
atom of water takes its r>lace, so that the tribasic type is retained : it is then called 
neutral phosphate of lime. By expelling another equivalent of lime, and replacing it by 
water, we get the superphosphate of lime ; — an equivalent of phosphoric acid, an equiva- 
lent of lime, and two of water. 

98. The tribasic phosphate, or "basic" phosphate, as it exists in bones or the mineral 
apatite, &c, is very insoluble in water, and therefore acts but slowly in the soil. To in- 
sure a more prompt effect, it is changed to the superphosphate. This is done by adding 
sulphuric acid to bone-dust, which takes away the lime from the phosphoric acid. A 
certain proportion of sulphuric acid removes two atoms of lhne ; thus changing the " basic " 
to the " super"phosphate. A larger quantity of sulphuric acid withdraws all the lime, and 
leaves the phosphoric acid. 

99. The salts of phosphorus are represented according to the old view ; but it will be 
seen that the acids are all changed to salts, by simply replacing their hydrogen by a 
metal. They may be expressed, according to the new view, by supposing the existence 
of three compound radicals, P0 6 , P0 7 , and P0 8 . These combine with hydrogen in 
the acids thus: HP0 6 , H 2 PO T , H 3 P0 8 ; and their salts (M standing for metal) will 
be M P0 6 , M 2 P0 7 , M 3 P0 8 . This view is preferred by Gregory and Liebig. 

100. We have seen that the elements are endowed with strong affinities, and unite in 
pairs to produce acids and basis ; these again have powerful tendencies to combination, 
and give rise to salts ; but at this point combining power nearly ceases. Salts, it is true, 
combine with each other to form double-salts, but by no means indiscriminately. With 
rare exceptions, the combining salts have all the same acids : sulphates combine with 
sulphates, and chlorides with chlorides. Their bases, or their metals, must, however, be 
widely different from each other. There is no resemblance between the structure of 
double-salts and that of simple salts themselves : one does not, as has been supposed, 
act the part of an acid, and another of a base. Examples of double-salts will be 
observed in Plate IV. 



101. The rocks which appear at the earth's surface, and which are said to compose its 
crust, are of two kinds. Some of them occur in sheets or layers (strata), of various thick- 
ness, and are called the stratified rocks ; others exhibit no evidence of layer-structure or 
stratification, but are found in great rounded or irregular masses, and are termed the un- 
stratified rocks. 

102. These two classes of rocks seem to have quite different origins. The unstratified 
rocks give evidence of having been formed by fire. They seem to have been melted, and 
to have cooled and assumed the crystalline state under great pressure, and not exposed to 
the air : they are therefore termed igneous rocks. The great mass of the stratified rocks, 
on the other hand, are not crystalline, and appear not to have been melted, or to afford 
any evidence of the action of fire. They give assurance of having been deposited from 
water, in the shape of sediment, which has been gradually solidified and hardened into 
rock by the pressure of the watery mass and other causes. They are therefore called 
aqueous or sedimentary rocks. 

103. The stratified rocks contain innumerable traces and remains of living beings, 
animals, and plants, which seem to have been imbedded or wrapped up in the sediment- 
ary matter as it has been deposited. These relics and vestiges are termed fossils, and the 
rocks which bear \hem fossiliferous rocks. We find nothing of this kind in the igneous 
or crystalline rocks. They are called non-fossiliferous or azoic (without life). 

104. There is a class of rocks which possesses the stratified arrangement, and yet con- 
tains no fossils : they are crystalline, and have evidently been acted upon by fire. They 
are considered as stratified, water-formed rocks, which have been changed or altered by 
heat, their fossils burnt out or obliterated, and their particles thrown into the crystalline 
order. They have obviously been metamorphosed, and are therefore named metamorphic 

105. Our knowledge of the strata has not been obtained by digging or excavating 
down through the successive layers. It so happens that the strata do not, except in rare 
cases, remain in the position . in which they were formed. They have been broken and 
thrust upward, so that their edges appear at the surface, or, as it is termed, " crop out." 
Had the rocks remained as they were deposited, we could know little or nothing of them. 
It is this circumstance of their inclined position, by which we can inspect them directly in 
passing over a country, that makes geology possible. 

106. It is believed that the changes which the earth's surface has undergone in past 
ages are of the same kind as those now going forward upon its surface. There is a ques- 
tion, however, as to the intensity with which forces have acted, and the speed with which 
alterations have occurred, in former times. It has been generally imagined, and many 
still suppose, that the earth was formerly the scene of agencies acting with vastly greater 
power and violence than they do now. Yet some of the profoundest inquirers of the 
present day think we need resort to no such hypothesis to explain the geological changes 
which the earth has undergone ; but that the forces now operating to alter and modify 



its surface at their present rates of activity are altogether adequate to have effected what 
ever has been done. 

107. It is demonstrated that the existing rocks are now wearing and wasting away, 
and that new ones are in process of formation. Various causes (141) are cooperating to 
decompose and disintegrate the rocky masses, and crumble them down into the condition 
of soil. Kunning water transports these loose materials to the lower levels, deposits them 
in the beds of lakes, rivers, and oceans, where they are gradually compressed and ce- 
mented into new rocks. By the present action of subterranean fire, as manifested in 
earthquakes and the throwing up of volcanic islands, these new layers are heaved from 
their beds, dislocated, and forced into all varieties of position. Slow sinkings and eleva- 
tions of vast tracts of land are also frequently noticed. And not only is the sea gradually 
filling up its bed with matter brought down from the continents, but by the undermining 
and lashing action of currents and waves, it in many places makes inroads upon the land, 
while in others it continually adds new matter to the beach, and thus slowly retires from 
the shore. Causes are therefore now at work, which require only the addition of the 
element of time to change the present continents to oceans, and the existing oceans to 
continents. Geologists find abundant evidence that great alterations of this kind have 
already taken place. Mr. Lyell says : " It can be shown that the earth's surface has 
been remodelled again and again ; mountain chains have been raised and sunk ; valleys 
formed, filled up, and then reexcavated ; sea and land have changed places ; yet through- 
out all these revolutions, and the consequent alterations of level and general climate, 
animal and vegetable life has been sustained." — Manual of Geology, p. 501. 

108. Now as these forces have been at work, and such effects produced actively and 
constantly in past time, it is evident that geological phenomena must present a progres- 
sive and successive order. There is an order of the rocks that corresponds to the 
order of time. There are earlier and later, older and newer rocks. They certainly 
could not have been contemporaneous in origin. Each formation (as a series of strata 
produced under the same general circumstances are termed) has therefore its "age" 
or " epoch," and the whole system a chronological order of succession. 

109. If, therefore, the rocks had a fixed order of occurrence — were successively 
formed — it follows that they must have a corresponding order of position. Succession of 
time involves succession of place. As there are older and newer rocks, so there are lower 
and higher rocks. The lower correspond to the older, and the higher to the more recent. 
If we represent the order of formation, beginning with the most ancient, by the numbers 
1, 2, 3, 4, 5, 6, the same arrangement of figures may represent the ascending series of 
those formations : as 6 is the latest, so it will also be the highest. This will illustrate 
what is meant by the order of superposition of rocks. 

110. It is not to be understood that all the rock-formations known are every where 
piled one above another, in a uniform, complete, and uninterrupted series. There is, 
indeed, no one place where the continuous and unbroken series can be observed. There 
is every where an absence of some of the members of the series : there are defects and 
gaps in it, but never an inversion of it. If we represent the order of position by the above- 
mentioned arrangement of numbers, then, in particular cases, we shall have a lack of some 







or Recent 






M *gnesian Um 


New Red 

ous System. 






phic Rocks. 







fcr 1 

I— I 







i— i 

The seven minerals whose com- 
position is represented below com- 
pose the great mass of the rocky- 
strata or formations of the earth's 

Quartz, {silica.) 


TALC, (SoajMone-) 










- — . . . 

Hornblende or Augite. 




Carbonate of Lime. 


of thein, as of formations 2 and 3 : formation 4 will then rest upon formation 1, and the 
actual order will be 1, 4, 5, 6. But although the order may be imperfect or deficient, we 
never find it contradicted, as, for example, 1, 3, 2, or 5, 4, 6. A formation may be found 
resting upon any which belougs below it, but it is never found beneath them. 

111. The completeness of the series is established by comparing the observations of 
various localities. If at one place formations 2 and 5 are missing, observation at another 
place may give formations 1, 2, 3, 4, and further investigation at other points present 
3, 4, 5, 6, by which the entire series is determined. 

112. As the series of formations is nowhere complete, and as the strata have been 
almost universally removed from the positions in which they were formed, the task of 
determining the true order, and of assigning to each its proper position, has been one 
of great labor and perplexity. Their aspects and properties, physical and chemical, have 
afforded aid in identifying and arranging them ; but the chief clew to their relationships 
has been found in the study of their fossils. So diverse and almost innumerable are the 
living tribes of plants and animals that inhabit earth, sea, and air, and so endlessly vary- 
ing in different portions of the globe, that we can easily understand how traces of these 
should become the peculiar characteristic marks of the rock-formations that retain them — 
the indices of the earth's earlier changes and conditions. They are the monuments of 
geological transition and progress, and have been aptly denominated the " medals of crea- 
tion." By the aid of these lights, science disentangles the curious history of the rocks, 
and establishes their true order. It has been said that the geologist proceeds to arrange 
the rocks as he would the loose and disordered leaves of an unpaged book, by means 
of the natural connection and continuity of its narrative or history. 

113. Plate IV. presents an ideal section of the earth's crust, in which all the forma- 
tions are supposed to be present in their true relative positions. At the right we see the 
successive layers that would be discovered by sinking a shaft downward, or cutting 
vertically through them. In consequence of their inclined positions, the same strata 
appear at the surface, and may there be observed in the same order. They are, however, 
much covered or masked at the surface, by beds of water and layers of soil, as is shown 
upon the diagram. The different formations are represented by different colors. 

114. Geologists agree upon the order and position of rocks, but not upon their classi- 
fication and nomenclature. They divide and name them differently. The system of 
division presented in Plate IV. is perhaps the one most generally received. 

115. It might be supposed that, in the immense mass of rocks which make up all the 
accessible parts of the earth's crust, there would be found the largest diversity of materials. 
Yet the bulk of all the great rock-formations consists of only about ten or twelve chemi- 
cal elements — the same which we have represented in the preceding plates. These 
elements unite in the form of minerals, and these minerals, either in their simple state, or 
combined together, or variously decomposed, give rise to the rocks. (The term " rock," in 
its geological acceptation, applies not only to the solidified stony-formations, but to less 
cohesive and compact structures, as sand and clay beds). 

116. Now the number of minerals known is quite large, and there prevails an impres- 
sion that in studying geology we encounter a formidable array of them. This is an error. 


The entire series of rock-formations with which Geology acquaints us, is constituted in the 
great mass of only seven simple minerals. These compose, at least, nineteen twentieths 
of all the geological systems. Other minerals, indeed, occur, distributed through the 
formations, but in comparatively minute quantities. 

117. The minerals that are of geological importance are : 1. Quartz; 2. Talc; 3. ter- 
pentine ; 4. Hornblende, or Augite ; 5. Feldspar ; 6. Mica ; 7. Carbonate of lime. The 
composition of these is presented in the geological chart (Plate IV.). 

118. Quartz is a mineral with which all are probably familiar. It is often seen in six- 
sided, transparent crystals, which scratch glass: they are picked up in the field, and are 
vulgarly called diamonds. It however exists in a great number of aspects, containing 
minute traces of various metals which impart varieties of color. It constitutes a large 
variety of precious stones. It is by far the most abundant mineral upon the globe: its 
two elements exist in the largest quantity of any which form the solid mass of our earth. 
It is more than half oxygen: there being 22 parts of silicon to 24 of the former element. 
It is called silica, or silex, and breaks or crumbles down into fine grains, which are called 
siliciovs sand — the most common and abundant of all the sands. These sands are some- 
times cemented together, or solidified to a stony hardness ; they then form siliciovs rocks 
or sandstone. 

119. Quartz or silica, in its ordinary form, is insoluble and inert; yet, when melted, 
it becomes an acid, combining with alkalies and metallic bases to form a large family of 
salts — the silicates. Thus glass results from the melting and union of silica with potash, 
soda, or lime : it is a true salt, silicate of potash, soda, or lime. Now, when combined in 
minerals, silica exists in the same relationship. It forms minerals by uniting with bases, 
which therefore have the saline constitution. 

120. Talc is a soft, pearly-looking, greenish-white mineral, with an unctuous or soapy 
feel. It is a silicate of magnesia. Serpentine is a silicate of magnesia, with oxide of iron. 
It is of a decided green color, often variegated or mottled. Hornblende is a dark green or 
black mineral — a triple silicate of iron, magnesia, and lime. Augite is identical with 
hornblende in composition, differing from it only in crystalline form. Feldspar is a reddish 
or flesh-colored mineral — a double silicate of alumina and potash. In different varieties 
the potash is replaced by soda or lime. Mica is a mineral made up of thin elastic plates 
or scales, which are easily separated, and is of a shining black, brown, or silver color. It 
is likewise of a saline structure — a silicate of potash, alumina, and iron. Carbonate of 
lime is found of nearly all colors and aspects, as chalk, marble, and limestone. It consists 
simply of carbonic acid and lime. 

121. The composition of all the above minerals is not settled with precision, as there 
is considerable variation in different samples. Other substances not mentioned are some- 
times found in them in small quantity ; but the diagrams of Plate IV. exhibit them with 
sufficient accuracy for purposes of general information. 

122. The structure of these minerals is placed before the eye in Plate IV., opposite 
the geological series to which they give rise. Let us now see how the rocks are consti- 
tuted of these mineralogical elements. The oldest and deepest rock is granite. It is 
primary, igneous, unstratified. It lies beneath all the other formations, and also rises 


above therm, constituting the highest summits and the rocky mass of the great mountain 
chains of the globe. The minerals which compose granite are quartz, feldspar, and mica. 
Distinct crystalline fragments of each mineral are perceptible in granite : when these are 
large, it is called coarse-grained ; when small, fine-grained. The proportion of these 
minerals may vary : when mica prevails, the rock has a dark color ; if feldspar abounds, 
it has a flesh-color; while, if quartz predominate, it has a whitish aspect. Sometimes 
hornblende is added to these regular constituents of granite ; we then have syenitic 
granite. If the hornblende is substituted for mica, we have syenite, composed of quartz, 
feldspar, and hornblende. If the rock contains numerous crystals of reddish feldspar, it 
is termed porpliyritio granite, or porphyry. 

123. Thus, in composition, granite is the most complex of rocks. It is oldest in the 
order of time, highest in position, and is known to contain very nearly, if not quite, all the 
elements which enter into the later formations. It is hence supjDosed to be the primal 
source from whence the materials of all the other and later rocks were derived. By 
decomposition, its quartz yields sand and sandstones, and the silicious elements of innu- 
merable rocks. Its feldspar and mica produce the clay of clay-beds, slates, and argilla- 
ceous rocks ; while the lime of limestones, chalks, marls, and calcarious rocks, may per- 
haps have come from those varieties of granite which contain this ingredient. 

124. The metamorphic rocks lie immediately above the granite. They consist of 
several members. Gneiss is a rock usually lying directly upon granite. It is similar to 
it in composition, and passes insensibly into it ; so that it is impossible often to determine 
the exact line which separates them. It consists of quartz, feldspar, and mica ; the feld- 
spar being less abundant than in granite, and the quartz in fine grains. The term gneiss 
is derived from a word signifying to sparkle ; the mica it contains giving it a glistening 
aspect. Gneiss has been called stratified granite. 

125. Gneiss often changes or passes into mica slate. In this rock the feldspar dis- 
appears, and the mica is more abundant. It possesses a more perfect slaty structure than 
gneiss ; that is, a capability of being split into leaves or lamina. Hornblende slate is com- 
posed principally of hornblende, with a variable quantity of feldspar, quartz, and mica. 
It often passes imperceptibly into mica slate. Talcose slate consists of talc, some- 
times pure, but often mingled with quartz, feldspar, and mica. Steatite, or soapstone, is 
a variety of this rock, of a grayish-green color, a " greasy feel," and consists largely of talc. 
Chlorite slate is another variety of the same rock. 

126. Clay slate, or argillaceous sliist, is found both in the metamorphic rocks and also 
higher up in the series. It consists of a very fine mixture of mica or talc, with quartz, 
a very large proportion of argillaceous matter, a little oxide of iron, and some of the 
alkaline earths. It often occurs interstratifled with mica slate and quartz rock ; and, in 
proportion to its nearness to granite or other igneous rocks, it becomes more highly 
glazed, changing gradually into talcose, hornblende, or mica slates. Passing in the other 
direction (higher up, or further from the fire-formed rocks), its lustre becomes more dull, 
and its texture less compact, — it is called shale : and still further up in the series it ex- 
hibits itself in beds of clay (St. John). 

127. Serpentine occurs as a stratified metamorphic rock. Quartz rock, when pure, has 


little or no tendency to stratification ; bnt when mixed with other minerals, as it often is, 
it tends to divide into parallel beds. 

128. Primary, or crystalline limestone, among the metamorphic rocks, occurs in thick 
beds, and in thin leaves, interstratified with gneiss, mica slate, and clay slate. It is a 
simple carbonate of lime, crystalline, close-grained, and pure white ; the foreign matters, 
which darken and discolor common limestone, having been burnt away by the heat to 
which this class of rocks has been subjected. 

129. With the igneous granite, and these metamorphic or fire-changed rocks, another 
class, formed by the agency of heat, may also be associated. They originally existed in 
the melted condition, and were thus thrust through and between the strata, in the form 
of dykes and veins. Prominent among these is the trap family ; so called from the word 
trappa, a stair ; because the molten mineral matter thrown up to the surface assumed, 
in cooling, the form of tabular masses, rising one above another, as terraces or steps. 
There are several varieties of trap rocks. Greenstone is of a dark-green color, either 
massive or in tables, and consists of an intimate mixture of feldspar and hornblende. 
Basalt, which is often found in regular pillars, called basaltic columns, consists of augite 
and hornblende. Trachyte is composed of feldspar, with a small proportion of horn- 
blende, iron, and mica. 

130. The lava from volcanoes is mainly composed of feldspar and hornblende, or 
augite, although many other simple minerals are found distributed through it. In the 
dark-colored lavas, augite is the leading ingredient ; in the light-colored lavas, feldspar 

131. Upon the metamorphic rests the silurian system; so called from the silures, an 
ancient tribe which inhabited a portion of Wales where these rocks were first investi- 
gated. This system is supposed to contain the oldest fossils ; that is, the earliest traces 
of organic life. It embraces numerous rocks, consisting of sand, clay, limestones, flagging- 
stones, and slates, some of which are very fine-grained. It also contains pebbles and 
fragments of rocks cemented together into what is called conglomerate. 

132. The Devonian system, or old-red sandstone, is composed of conglomerates, sand- 
stones, and marls, which consist of calcarious (limey) matter, mixed with a large pro- 
portion of clay or other earthy substance. The prevalent color of its marls and sand- 
stones is a dull-red, due to the peroxide of iron. It is called old-red sandstone, to 
distinguish it from the new-red sandstone, which is higher in the series. It is known 
also as the Devonian system, because it was first thoroughly studied in Devonshire, 

133. The carboniferous (coal-bearing) system consists of limestones alternating with 
sandstones and shales, which consist of hardened, slaty clay. These are interstratified 
with beds of coal, derived from an ancient vegetation, and containing very many fossil 

134. Upon the carboniferous system rests the new-red sandstone, lower and upper ; 
the lower being also termed the permian system, and the higher the triassic system. 
The leading member of the lower new-red sandstone is the magnesian limestone — a rock 
composed of carbonate of lime and carbonate of magnesia, and known as Dolomite. It 


also contains marls, with red and green sandstones. The upper new-red contains marls, 
sandstones, of various colors, chiefly red, and quartz conglomerate. 

135. Next in order occurs the oolitic system. Its lower member, the lias formation, 
consists of argillaceous limestone, and beds of marly sandstones alternating with clays. 
The higher divisions of this group consist of blue and yellow clays, calcarious sandstones, 
and coarse limestone, abounding in shells. The term oolitic is derived from oon, an egg, 
and litlws, a stone, from the fact that some of its beds resemble in appearance the eggs or 
roe of a fish. 

136. The cretaceous or chalk system takes its name from its leading member the chalk, 
which is a familiar earthy form of the carbonate of lime. Silicious stones in the form of 
rounded masses (nodules) of flint are interspersed through the chalk beds. This forma- 
tion also contains thick beds of marly clay and imperfect limestone, together with 
greensand beds, which consist of silicious sand mixed with silicate of iron. 

137. Next in the ascending order is the tertiary formation. This consists of sand and 
clay beds, and limestones, of various degrees of compactness, sandstones and buhrstones 
or millstone grit, a porous silicious rock. The sands and clays predominate, and the 
beds are generally more horizontal than those of the older formations. The tertiary is 
divided into eocene, mieocene, and pliocene ' a division based upon the distribution of 

138. Above all the rest, highest in the order of position, and latest in the order of 
time, appears the quaternary formation. It consists of two members called diluvium and 
alluvium. The lowest diluvium comprises beds of marl, sand, gravel, pebbles and clay, 
and also great numbers of bowlders, which are fragments of rocks of various sizes that 
have been torn from ledges, and transported or drifted to various distances. The 
alluvium, which is the formation now progressing, and which has been in progress since 
man inhabited the planet, consists of sands, gravel, clays, marls, peat, soil, and various 
forms of vegetable and animal matter, which streams, rivers, lakes, seas, and coral reefs 
are constantly accumulating. 

139. It will be seen that this vast series of geological structures consists of continual 
repetitions, in different forms, of the same mineral materials. The only additional beds 
of different composition in any considerable quantity are those of rock-salt (common 
salt), found in the new-red sandstone and cretaceous systems, and those of gypsum in the 
silurian new-red sandstone and tertiary formations. All the other rocks are but modifi- 
cations of the same few simple ingredients. 

140. In the diagram (Plate IV.) the formations are represented as passing upward in 
an inclined direction to the surface of the earth. It is not intended to show the exact 
degree of inclination, for this varies in all possible ways. These several formations are 
spread over large areas of country, and give particular geological characters to the regions 
where they exist. 

141. As has been said, the rock formations are undergoing perpetual changes through 
the action of fire beneath, and of various agencies above. By the contractions and expan- 
sions of heat and cold, by the wearing action of waters in motion, by the penetration of 
moisture into the pores or interstices of stones, and its after expansion in freezing, the 



surface of rocks is broken and crumbled away, sometimes, indeed, very slowly, but ofteii 
with much rapidity. 

142. The same effects are produced by other destructive causes, which spring out of 
the chemical composition of rocks on the one hand, and of the air on the other. The 
atmosphere contains from l-1000th to l-2000th of its bulk of carbonic acid, a gas of 
which water absorbs a large amount. All the water which falls from the clouds there- 
fore contains it. Carbonic acid is also formed in the earth in immense quantities, and 
the waters of springs come up to the surface charged with it in various proportions. Now 
water containing carbonic acid possesses a remarkable power of dissolving and destroying 
stones. It has been shown by extensive experiments, that no species of rock whatever 
will resist the solvent action of water impregnated with carbonic acid. Artificial mineral 
waters are made by bringing various minerals into contact with water containing carbonic 
acid, which dissolves out their salts, and thus acquires new properties. 

143. Water charged with carbonic acid acts differently upon different rocks. The 
chalk, marbles, marls, and entire limestone family, are simply dissolved, and may be 
again precipitated and hardened into calcarious rock. But the action of carbonic acid 
upon granite is of a different nature : it here acts to break up the chemical unity of the 
rock, by decomposing it and separating its elements. It is because the minerals which 
compose these rocks — serpentine, hornblende, feldspar, and mica — are saline in their com- 
position ; because they consist of bases united to an acid, with an affinity so feeble that 
carbonic acid is able to overcome it : this is the reason of these decompositions. The 
carbonic acid combines with the alkalies, forming carbonates, which are dissolved in 
water, and borne away perhaps to the sea. The unity of the minerals is thus broken ; 
the silica and alumina (sand and clay) are set free, and being insoluble in water, accumu- 
late, and thus constitute the essential basis of soils. 

144. In Plate II., the chief mineral constituents of soils are seen to be arranged in 
four pairs, namely, a pair of alkalies, of alkaline earths, of earths, and of metallic oxides. 
Manganese in minerals is often associated with iron : it exists in small quantity, but is 
very widely disseminated. These few ingredients of soil are indispensable to the growth 
of plants, and consequently to all life ; and are thus derived, by forces now in action, from 
rocks that are universally distributed over the earth. 

145. But in the crumbling down of rocks into the mixtures of soil the decomposition 
is not complete. Beside a portion of alkalies and alkaline earths lingering free in the 
soil, the sands and clays contain large amounts of potash, soda, lime, and magnesia, locked 
up in combination, so as to be imperfectly, or not at all available to growing vegetation. 
Yet the same forces which disintegrated the rocks are still at work upon these constitu- 
ents of soils. It is one of the chief benefits of mechanical culture with the plow and other 
implements to loosen the soil, so that air and moisture can get access to it, to carry for- 
ward the same decomposing changes, liberating the needed elements of fertility, so that 
they may become available for vegetable nourishment. 

146. Hence, also, the import of "fallow," by which the farmer means the rest of land 
after a series of crops. But the powers of nature never get fatigued : the true explanation 
is, that the soluble constituents are removed from the soil by successive crops, until 


remunerating growths can no longer be obtained. Time must then be allowed for the 
elements of fertility to be again set free, wlien the land is said to be m fallow. Fallowing 
is now much less in use among farmers than formerly : it is superseded by systematic 
rotations of crops ; that is, instead of letting the ground remain idle, such a crop is taken 
from it as will not require the missing constituents of the soil. 

147. As there is considerable variation in the chemical composition of rocks, so there 
will be a corresponding variation in the compositions of the soils derived from them. For 
example, the slates and feldspathic rocks, when reduced, give rise to argillaceous soils, or 
those in which clay predominates ; the sandstones produce silicious soils, those abounding 
in sand ; and decayed limestone forms calcarious soils, or those characterized by a large 
proportion of lime. Now, as the agricultural capabilities and adaptation of soils to the 
growth of special crops depends primarily upon chemical constitution, it is easy to see 
that, through Chemistry, agriculture has a relation to Geology. Nevertheless, in fact the 
problem of this relation is a very complicated one ; for there has been such transporta- 
tions and admixtures of materials of soil, that it is frequently difficult to trace it to its 
parent rock. Geology is undoubtedly capable of affording important contributions to 
agricultural science ; but a considerable degree of knowledge, and much caution in judg- 
ment, are required to make these contributions practically available. 




148. Organic Chemistry is that branch of the science which considers the composition, 
properties, and changes of organized substances, or those which have originated in living 
beings, or been derived from them. It embraces a highly interesting portion of the 
science ; for to a living, conscious being, all that appertains to life, its conditions and 
laws, must have a profound concern. My treatment of this part of the subject, also, must 
be mainly confined to such points as may be illustrated by diagrams — the reader being 
referred to the class-book for its more general consideration. 

149. The first fact which claims our attention, is the exceedingly small number of ele- 
mentary bodies that are brought into notice in this department of the science. Four 
elements mainly constitute organic structures, and bring about organic changes : these are 
carbon, oxygen, hydrogen, and nitrogen, — from this circumstance called organogens (gen- 
erators of organization). In addition to these, minute proportions of sulphur, phosphorus, 
potash, soda, iron, and lime, are found in organic substances, and which appear as ash 
after their combustion. These, though important, exist in very small proportion — so 
small, indeed, as to have been formerly thought accidental ingredients of organized com- 
pounds — mere impurities. We pass them by, and give our attention to the four organic 

150. Of these, three are gases ; and one, carbon, is a solid — in its free state, for ever a 
solid. The other organic elements — oxygen, hydrogen, nitrogen — may be present, either 
or all, in organic compounds ; but carbon is always present. It exists in every organized 
substance ; so that this branch of the science has been defined as the chemistry of carbon 

151. From these four constituents the world of life springs into being. This fact is 
more than wonderful, it is amazing ! That the countless tribes of beings, vegetable and 
animal, which inhabit all the climates of the earth, varying almost infinitely in their 
attributes and powers, and giving rise to numberless natural products, which are multi- 
plied by art without end, should be made up by the combinations and permutations of 
only four kinds of matter, is assuredly the standing marvel of time ! Nevertheless, we 








S r 




Oil of Lemons. Oil of Bergamot. 

4v"4> ■ 
■Jl^« ■ ■ ■ 
▼■♦ " B " 

Oil of Turpentine. Oil of Black Pepper. 

(Spirits of Turpentine.) 


k Acetic Ether. 



Oil of Juniper. 


■ -■ 

Oil of Oranges. 



■ «■ 

■ -■ 


Oil of Peppermint. 

Oil of Copaiba. 

Oil of Eoses. 


m || 

■ ■ 

■ II ■ 



Oil of Limes. 

Olefiant G-as. 

Oil of Lavender. 


are not without some clew to the method by which such august results are brought about 
by so apparently trifling and insignificant means. 

152. Many organic compounds are derived from the four elements, by variations m 
the proportions in which these elements combine. Organic substances may consist of either 
two, three, or four different elements, and may contain of these from three or four atoms 
up to several hundred. The possible difference in the proportion of the organic con- 
stituents is therefore very great. The slightest alteration in the proportion of a single 
element, is sufficient to change the nature and properties of a compound. 

153. But we are not really restricted to four organic elements ; by a wonderful 
device, these elements are capable, in effect, of being largely multiplied. The same 
element is capable of existing in several states, so totally different in properties, as to 
appear like different substances. Carbon, for example, manifests itself under the form 
of an opaque jet-black powder or dust, lamp-black, which is so highly inflammable as 
to take fire often spontaneously in the air ; and it also appears as that transparent and 
most beautiful of gems, and hardest of minerals, the diamond, which is also so extremely 
incombustible, that it is difficult to burn it even in oxygen gas. Charcoal, anthracite, 
gas-carbon, and black lead, are other and dissimilar states of the same element, which 
certainly differ from each other in aspect and apparent properties more widely than some 
known elements, especially the metals, differ among themselves. 

154. These remarkable conditions of the elements are termed allotropic states. It 
is said that all the elements, except hydrogen, are subject to this modification ; and it 
has been lately announced that an allotropic condition of hydrogen is also discovered. 

155. Now it is easy to see that we have here another possible source of variation in 
the properties of chemical compounds. We may consider the substances of identical 
composition, and yet having different properties. We have but to suppose that the 
elements carry their allotropic conditions with them when they enter into union, and 
although proportions are identical, there may obviously be wide difference of properties. 
Thus we may have two compounds of carbon and hydrogen, both in exactly equal pro- 
portions, but if the carbon enters into one as charcoal, and into the other as diamond or 
anthracite, the same result may be produced as if two distinct elements had been 

156. The phenomena of allotropism are exceedingly interesting, and engage increas- 
ingly the attention of chemists. It is by no means improbable that their elucidation 
will yet throw much light upon the relations of chemistry to vegetable and animal 

157. But the variations in the properties of organic compounds are to be mainly 
explained by difference in the grouping of their elementary atoms. Indeed, the science 
of organic chemistry is little else than a study of the groupings of atoms. In inorganic 
chemistry we find the character of compound bodies depending chiefly upon the nature 
of their elements, but the properties of organic compounds are determined less by what 
their elements are than by the way in which they are arranged. The leading mark of 
distinction between potash and soda is, that one contains potassium and the other 
sodium ; but between oil of lemons and spirits of turpentine there is no such distinction. 


Their elements are of the same nature, and name, and properties ; they differ only in 

158. The statement that two or more compounds may consist of the same elements, 
united in exactly the same proportions, and yet have unlike properties, would have been 
regarded a few years ago as chemical heresy ; but it is now universally recognized as a 
fact. It was supposed that difference of properties necessarily implied difference of 
chemical constitution, but analysis most carefully conducted, and many times repeated, 
has established that there may be difference of properties with identical composition. 
Two substances different in attributes will yield on examination equal proportions of the 
same products. The term isomeric from isos equal, and metrom measure, is used to 
designate this class of compounds. 

159. The fact of isomerism rests upon evidence more positive even than that of 
analysis ; these compounds can be converted, and reconverted into each other without 
addition and without subtraction. In cyanuric acid, hydrated cyanic acid, and cyamelide, 
we have three such isomeric compounds. Cyanuric acid is crystalline, soluble in water, 
and capable of forming salts with metallic oxides. Hydrated cyanic acid is a volatile, 
and highly corrosive fluid, which cannot be brought into contact with water without being 
instantaneously decomposed. Cyamelide is a white substance very like porcelain, absolutely 
insoluble in water. 

160. Now if we place the first, cyanic acid, in a vessel perfectly (hermetically) 
sealed, and apply a high degree of heat, it is converted by that influence into hydrated 
cyanic acid ; and then, if this is kept for some time at the same temperature it passes 
into cyamelide, no constituent being separated, nor any substance being taken up from 
without ; and again, inversely, cyamelide can be converted into cyanuric acid and hydrated 
cyanic acid (Llebig). 

161. These changes and differences of properties are believed to be due to differences 
in the position and arrangement of the constituent atoms. As the power and effectiveness 
(properties) of an army may depend upon the arrangement and distribution of its 
soldiers, the same number of which may be thrown into innumerable positions, so dif- 
ferent groupings of the same chemical elements may form compounds very different in 
their powers and properties. 

162. Where the elements of two compounds are in different quantities, yet in the 
same relative proportions, affording the same results when considered in parts per hundred, 
the compounds are said to be polymeric. In Plate V. aldehyde, C 4 H 4 2 , and acetic 
ether C 8 H 8 4 , are examples of polymerism. The latter contains just twice as many atoms 
of each element as the former, yet their proportions per cent, are the same. Oil of pepper- 
mint C 10 H 10 O, and oil of lavender C 20 Il2o0 2 , are also illustrations of polymerism. 

163. Where compounds possess the same absolute composition, or equal numbers of 
atoms, their difference of properties is more manifestly due to alterations of grouping, 
and they are said to be metameric. Plate V. exhibits a series of eight hydrocarbon 
compounds, commonly represented by the formula C 5 H 4 , although some of them may 
prove to be polymeric with these proportions. They are oil of juniper, oil of black 
pepper, oil of turpentine (spirits of turpentine), oil of bergamot, oil of lemons, oil of 




Oxide of Ethyle. 

Hylrated Oxide 
of Ethyle. 




Terciiloride of 



Acetyl e. 

Hydrated Protoxide 
of Acetyls. 


Hydrated Deutoxide 
of Acetyle. 

(Acetylous Acid.) 


Hydrated Peroxide 
of Acetyle. 

(Acetyllc Acid, Vinegar.) 


■ ■■ 

■ ■ 

An atom of ethyle 
replaces an atom of 
j hydrogen. 


Ethyl amine. 

i b i 


Two atoms of Ethyle 
?■ replace two of hydro- 
is 1 gen. 

'5 J ° 




■ I ■ 


■ ■ 

■ ■■■■ 


■ ■■■ 

"1 Three atoms of 
ethyle replace 
three of hydro- 

j gem 



Ethylo-methylo-propylamine. J and propyle 

s "] In this case, the hydrogen of 

! the ammonia is replaced by 

■ r three different compound 

I radicals — ethyle, methyle, 




(Benzoic Acid.) 


Hydrated Peroxide of Formyle. 

(Formic Acid.) 




copaiva, oil of limes, and oil of oranges (the rind). I need hardly say that the diagrams 
do not attempt to express the manner in which the atoms may be really arranged, but 
only to illustrate the idea of variable grouping. 


164. This theory, in all its applications, is an illustration of the important part played 
by groups of atoms in organic chemistry. It has been already alluded to (87). The 
doctrine supposes that certain combinations or groups of elements take on the properties, 
and play the parts, of simple bodies, so that we may trace them in their relationships and 
changes as we do the simple bodies of inorganic chemistry. Potassium, for example, is an 
element; it combines with oxygen, forming oxide of potassium. This compound com- 
bines again with water, forming hydrated oxide of potassium. If, in place of water, we 
employ nitric acid, we get nitrate of oxide of potassium ; or with other acids, a large class 
of salts of oxide of potassium. Now potassium is here evidently the starting point, the 
foundation, the root, the radical of this series ; and as it is undecomposable, it is called a 
simple radical. 

165. Now there are compounds that behave in the same way, and are hence called 
compound radicals. According to this view, all organic substances are made up by com- 
binations of these radicals with each other, and with simple elements, in the same manner 
as acids and salts. Illustrations of this theory are shown on plate VI. Ethyle is a com- 
pound radical, consisting of four atoms of carbon and five of hydrogen, and comporting 
itself like a metal. It is the root of a large series of compounds. Common ether (sul- 
phuric ether) appears to be an oxide of ethyle ; and, with the addition to it of an atom 
of water, we get hydrated oxide of ethyle, or common alcohol. 

166. Formyle (Plate VI.) is a compound radical C 2 H, which forms also a large series 
of compounds, of which only the most important — chloroform and formic acid — are given. 
In chemical language, and according to this theory, chloroform is the perchloride of for- 
myle. Another organic radical, represented in Plate VI., is acetyle C 4 H 3 . Aldehyde 
is seen to be a hydrated protoxide of acetyle ; acetylous acid is a hydrated deutoxide of 
acetyle ; acetylic acid — acetic acid, or vinegar — is a hydrated peroxide of acetyle. 

167. A few organic radicals are known in the separate state, but most of them have 
not been thus obtained. Ethyle, for example, has been set free, while formyle and ace- 
tyle have not. They are decomposed in the act of separation. The adherents of this 
theory hold that the fact of the non-separation of the great majority of organic radicals 
affords no objection to their existence and importance. They assert, first, that such things 
as compound organic radicals do exist in the isolated condition ; second, that there is 
strong warrant for believing that numerous others which have not been, or perhaps can- 
not be separated, do exist ; and, third, that their assumed existence is of great convenience 
in study, in classifying the facts of the science, in assisting the memory, and in exhibiting 
organic changes in the clearest light. 



168. The theory of organic radicals has been most current in England and Germany. 
The French have attempted to explain organic compositions and changes by the theory 
of types and substitution, which has won its way to considerable favor. Like the doc- 
trine of compound radicals, it is only important as an instrument of abstruse study, and I 
shall therefore pass it with but a brief explanation. Both doctrines spring from the 
necessity of finding some relationship among the crowd of facts which are incessantly 
accumulating in organic chemistry, and which must be in some way arranged and asso- 
ciated, so as to become manageable by the mind. 

169. A chemical type is a compound which, in composition or properties, may repre- 
sent or symbolize a class, and which admits of the exchange or substitution of its elements 
without destruction of its typical character. Thus, in inorganic chemistry, we may say, 
for example, that hydrochloric acid is the type of a numerous class of acids, the character 
of which is, that they contain hydrogen united to a salt-radical. If for chlorine we sub- 
stitute iodine, bromine, or cyanogen, the type remains unchanged — the compound is still 
an acid analogous to that which was selected as the type. 

170. Again, common salt, Na CI, is the type of a very large series of salts, in which a 
metal is united with a salt-radical ; and if we substitute potassium, lead, or silver, for the 
sodium ; or iodine, bromine, or cyanogen, for the chlorine, the type is unaltered : we obtain 
different salts, but still a salt of the type represented by Na CI. 

171. In organic chemistry, also, types exist in which replacement and substitution 
occur, while the typical attributes remain. Thus in acetic acid (Plate VI.), the three 
atoms of hydrogen may be replaced by three atoms of chlorine, in which the type is so 
little affected that the new substance, chloroacetic acid, has properties highly analogous to 
acetic acid. Again, in aldehyde, the three equivalents of hydrogen in the radical C 4 H 3 
may be replaced by three of chlorine, forming chloral — a body of the same type as 

172. It has been recently shown, moreover, by Wuktz and Hoffman, that the hydro- 
gen of ammonia may be partially or entirely replaced by compound groups of atoms, or 
organic radicals, without destroying the basic and typical character of the ammonia, I 
have represented this interesting substitution in Plate VI. A single atom of hydrogen 
of the ammonia is seen to be replaced by the compound radical ethyle, forming ethyla- 
mine. Two atoms of ethyle substituted for two atoms of hydrogen, forms diethylamine ; 
and three atoms of ethyle replacing all the hydrogen of ammonia, yields triethylamine. 
Again, the three atoms of hydrogen in ammonia are seen to be replaced by three different 
compound radicals, ethyle, methyle, and propyle, forming ethylo-methylo-propylamine. 
And what is most singular, these compounds so strongly resemble ammonia in properties, 
as to have been frequently taken for it, and thus overlooked when occurring accidentally. 

173. It has been supposed that the elements in inorganic types are in opposite electri- 
cal states — the sodium, or metal, in the common salt type, being in the positive state, or 
electro-positive ; and the chlorine, or salt-radical, being in the negative state, or electro- 



C 2 H 2 is the common difference, that is, each member of the series differs from the one preceding 
it and the one following it by two equivalents of Carbon and two of Hydrogen. 

Formic Acid, d H 2 4 

Acetic Acid, d H 4 O4 

Propylic Acid, d H 6 4 

Butyric Acid, C s H s O4 

Valerianic Acid, do H10 4 

Caproic Acid, Cm Hm 4 

JSnanthylic Acid, Om Hi 4 4 




Caprylic Acid, 0i6 Hi 6 4 

Pelargonic Acid, da His 4 

Capric Acid, do H20 4 



Margaritic Acid, C 22 H 22 4 

Laurostearic Acid 


H 24 4 

Cocinic Acid, - - 

C 2 6 

H 2 6 O4 

Myristic Acid, 

C 2 s 

H 28 4 

Benic Acid, - - - 


H 30 O4 

Ethalic Acid, - - 


H 82 4 

Margaric Acid, - 

C3 4 

H34 O4 

Bassic Acid, - - 


II36 O4 

Balenic Acid, - - 


Has O4 

* * * * 


% •'.- 

Behenic Acid, - - 

C 4 2 

H 42 o 4 

H: H' ♦ # 


jfc -A' 

Cerotic Acid, - - 


H54 04 

* * * * 


* * 

Melissic Acid, - - 


Hoo 4 


negative: electrical conditions being assumed as the cause of chemical combination (36). 
This holds generally true in inorganic chemistry; but it entirely fails when applied to 
organic types. According to the electro-chemical hypothesis, hydrogen is strongly 
electro-negative ; hence, in inorganic types, they are incapable of replacing each other ; 
but, as we have seen (171), chlorine may replace hydrogen in an organic type, without 
destroying its properties, which contravenes entirely the electro-chemical theory. 


174. The progress of organic chemistry has recently revealed certain remarkable facts 
of combination, which are described as the pairing, coupling, or conjugation of compounds. 
In contradiction of a fundamental principle of inorganic chemistry, we here see two com- 
pounds combine, while one only loses its properties. In true inorganic combination 
(14-16) the properties of both constituents disappear, giving place to new properties in 
the compound. But in the phenomena of coupling, while one compound loses its pro- 
perties completely, the other entirely retains its properties — is unchanged by the union. 
The compound which loses its properties, or disappears, is called the copula, pa/i/rl/mg, or* 

175. Thus the compound benzoile (benzoic acid), (Plate VI.) combines with formic 
acid to produce formobenzoic acid, which in its character as an acid agrees entirely 
with formic acid, without possessing any of the properties of the benzoic acid. The for- 
mic acid has been retained ; the benzoile has lost its chemical character in the new com- 
pound. Formobenzoic acid is therefore regarded as a coupled acid, in which benzoic 
acid is the copula or pairling. 

176. There is reason to believe that this principle is brought largely into action in 
the formative processes of vegetable growth, by which the more complex bodies are 
derived from combinations of the lower and simpler compounds. 


177. Homology is a term used to express a curious relationship among organic sub- 
stances, which is so general, and of such simplicity, as to have been made by Gerhardt 
the basis of classification in his published system of chemistry. Homology implies the 
existence of compounds in series. A series of compounds is called homologous, when 
each member of the series, that is, each compound differs from the others, either by a 
certain number of atoms of carbon and hydrogen, or by a multiple of it ; and when the 
properties of these different compounds are entirely analogous, yet differ in degree, and 
that in proportion to the amount of carbon and hydrogen. 

178. Plate VII. represents the most remarkable of these homologous series. It 
consists of volatile acids. The difference between each compound of the series, and any 
other, is either two atoms of carbon and two of hydrogen (C 2 H 2 ), or a multiple of 


these. The proportion of oxygen is alike in all ; but from the starting point of the series, 
onward, we add C 2 H 2 , at each successive step, as will be seen by counting the equiva- 
lents or atoms. 

179. Now accompanying this singular homology of constitution, there is a remark- 
able analogy of properties. All the compounds of the series are volatile (see Class-Book, 
volatile oils). All but the two first are oily, and they increase in solidity, and their 
melting and boiling points rise with each successive increase of the common difference, 

G 2 H2 • 

1 80. It will be noticed that the present series has been carried up uninterruptedly to 
thirty-eight atoms of carbon, that is, compounds have been discovered, which by their 
composition arrange themselves in this order. Above this we notice interruptions, or 
gaps, which are not filled up. It is believed that compounds belonging in these intervals 
exist, and will be discovered. Only a few years ago but two members of this series were 
known, acetic and formic acids. The links have, however, been rapidly supplied, and the 
chain extended. 

181. There are many other homologous series known, but they are not complete in 
all their terms. It is thought that most, and perhaps all organic compounds belong to 

•such orders, and when two members of a series are determined, the others are confidently 
expected in the course of discovery. 


182. It is the grand office of the vegetable kingdom to organize inorganic matter; 
that is, to form out of dead mineral substances, earth, water, and air, compounds endowed 
with living or vital properties, and that are capable of forming the structures of animal 
systems. The substances which the plant makes use of, its nourishment, or the raw 
materials which it employs, are very simple in chemical character, and consequently, of a 
fixed, enduring nature. The peculiar compounds on the contrary, which the plant pro- 
duces, are of a much more complicated nature, hence easily deranged, and as a further 
consequence transient and unstable.* 

183. The organic compounds generated in plants are exceedingly numerous, and 
possess a vast variety of .properties. But few of these, however, very few, are employed 
by animals as food. It is true that a great number of plants are made use of as sources 
of nourishment ; but they all yield the same few vegetable principles or nutritive com- 
pounds, that life demands universally. These principles of nourishment, furnished by 
vegetation all over the world, are starch, sugar, gum, lignin, oil or fat, vegetable acids 
and albumen or the albuminous group as they are termed, gluten, fibrin and casein. 
Plants form these from the mineral materials which they draw upward from the soil by 
their roots, and absorb from the air by their leaves. 

184. The plant is thus the factory of organization. It elaborates or manufactures 

* For a much fuller consideration of this part of the subject, see Class-Boojc of Chemistry, 



Elements of Respiration and Calorification — their Source and Composition. 

Vegetable Acids. 

Two atoms of carbonic 
acid, from which one 
atom of oxygen is re- 
moved, produce oxalic 

Oxalic Acid. 

Malic Acid. 

Tartaric Acid. 


Carbonic Acid. 


I- 1 

1 V 

An atom of oxygen 
removed from an 
atom of carbonic acid, 
and replaced by the 
hydrogen of an atom 
of water, gives rise 
to an atom of sugar 
in its simplest form. 

Fruit Sugar. 

{Grape Sugar.) 
{Milk Sugar.) 

■ ■ 

Starch and 

> Woody -Fibre. 

Oils and Fats. 




■ ■■ 




■ ■■ 

■ ■■ 

■ ■■ 

■ ■■ 

■ ■■ 


Stearic Acid. 


Margaric Acid. 


■ ■ 


Citric Acid. 

Oleic Acid. 


material for the animal to appropriate and consume. The animal possesses no power of 
creating or constructing the substances which it needs out of decomposed inorganic matter. 
Though the animal feeds exclusively on flesh, yet that flesh was organized in the plants ; 
it is organic matter not yet destroyed, and which is used over again, by a second 
organism. The animal continually receives, transforms, and destroys ; it is the plant that 
combines and creates. 

185. The vegetable compounds above enumerated as being of importance to us in a 
dietetical point of view, are divided into two classes, which depend upon the presence or 
absence of nitrogen as an element of their composition. Those containing it are termed 
nitrogenized principles ; those lacking it, non-nitrogenized principles. 

186. The carbon of all parts and constituents of vegetables, and through vegetables 
of animals is derived from carbonic acid ; all the hydrogen of non-nitrogenized organic 
bodies (starch, sugar, woody fibre, gum and oil), is derived from %oater, and all the nitrogen 
of nitrogenized organic bodies is obtained from ammonia (Liebio). 

187. Under the influence of the radiant forces of the sun (275) acting upon the green 
leaf, carbonic acid, water, and ammonia are decomposed, and their atoms thrown into 
new positions and groupings, constituting the above-mentioned organized compounds. 

188. Plate VIII. exhibits the composition and source of those non-nitrogenized 
bodies, which are important to us from being universally employed as food. They are 
called ternary because they consist of but three elements. They are divided into three 
groups, which differ from each other in composition and properties, although the com- 
pounds of the same group have a similarity of properties. There is the vegetable acid 
group, the neutral ternary group (sugar, starch, <fec), and the fat and oil group. These 
are all derived, as has been said, from carbonic acid and water, which are decomposed 
in the plant, the oxygen being separated and thrown into the air, as is shown by the 
arrows pointing upwards in the diagram. Those pointing downward represent combina- 
tion. As these compounds are all derived from carbonic acid and water by decomposi- 
tion and grouping in the vegetable, so they all, by decay and destruction, finally return 
again to those simple conditions. 

189. An atom of carbonic acid (Plate VIII.) is a group of three elementary atoms, 
of which one is a carbon atom, and two are oxygen atoms. Now carbon, as has been said, 
exists combined with other elements in every organized compound. But no vegetable 
or animal substance contains for one atom of carbon more than two atoms of another 
element. The great majority of organic bodies contain for one atom of carbon less than 
two atoms of another element. 

190. Now all organized compounds may be looked upon as formed of atoms of 
carbonic acid, more or less altered or modified, or of groups of such modified carbonic 
acid atoms. This change or modification is the result of a separation of part of the 
oxygen of the carbonic acid atoms, in the place of which oxygen there is taken up hydro- 
gen, or hydrogen and nitrogen. The oxygen thus separated is expelled from the leaf into 
the air in a pure state. 

191. The simplest case of the production of an organized compound from carbonic 
acid in this manner, is perhaps furnished by oxalic acid. This substance belongs to the 


group of organic acids, and is found in combination with potash, lime, &c, in the leaves 
and stalks of certain plants. By reference to Plate VIII. it will be seen that oxalic acid 
consists of two atoms of carbonic acid united, from one of which an atom of oxygen has 
been removed. It is 2 C0 2 — O two of carbonic acid, minus one of oxygen. Oxalic acid 
is thus formed by reducing one atom of carbonic acid to half its natural quantity of 
oxygen, and joining that product to a whole atom of carbonic acid. 

192. This exhibits the starting point of organization, and discloses the essential office 
of vegetation. Plants are universally machines for separating oxygen — machines of 
de-oxidation. It is through these operations of de-oxidation and reduction, and by 
grouping together the products thus formed, that the plant becomes a builder and con- 
structer of organized substances. 

193. In malic acid, which exists in the apple and numerous fruits, we have not only 
de-oxidation, but a replacement of oxygen atoms by those of hydrogen. The source 
of the hydrogen is the decomposition of water, from which it was reduced by de-oxi- 
dation. If to a group of two atoms of oxalic acid, two atoms of hydrogen be added, 
and from the whole two atoms of oxygen be removed, malic acid is the result, the com- 
position of which is C 4 H 2 4 ; or double this formula C 8 H 4 O s , as it is commonly given. 
To make the changes seem as clear as possible, I have represented acids in the dia- 
gram as dry or anhydrous — that is, free of water. Nevertheless, these and most other 
organic acids exist in union with one, two, or three atoms of water, which appears, as in 
the case of the mineral acids (86), to perform the part of a base, so that malic acid, tartaric 
acid, &c. are, really malate and tartrate of water. They form salts by the replacement 
of their water by bases, or, their hydrogen by metals, according as we adopt one or other 
views of the structure of acids and salts. Oxalic and mahc acids contain each two atoms 
of basic water. 

194. In the same manner, by de-oxidation of carbonic acid and water, and the group- 
ing of the products, all the organic acids may be derived. It will be noticed as a fact 
characteristic of their general composition, that they contain only a small quantity of 
hydrogen, but a very considerable proportion of oxygen. The de-oxidating process has 
therefore not been carried very far ; most of the carbonic acid atoms may be supposed to 
have lost but half their oxygen, and but few water atoms have been split to furnish 

195. The neutral ternary compounds, sugar, starch, gums, &c, have as a class a dif- 
ferent composition from the vegetable acids. They are formed in the same manner, but 
the operation is carried further. They all agree in containing precisely the same pro- 
portion of atoms of carbon, each compound atom possessing twelve of this element. Of 
hydrogen and oxygen they contain an equal number of atoms, that is, for every atom of 
hydrogen there is one of oxygen ; these elements are in the exact proportion to form 
water. The quantity of these constituents, however, varies. Grape sugar contains twelve 
atoms of hydrogen and twelve of oxygen, while cane sugar and gum have but eleven, 
aid starch and lignum (woody fibre) but ten, atoms of each. 

196. Viewed in the simplest way, and with reference to the probable manner of its 
production, an atom of grape sugar, for example, may be regarded as an atom of carbonic 


acid, in which one atom of oxygen has been removed, and replaced by one hydrogen 
atom. These changes are very clearly shown by the diagram (Plate VIII.) The direc- 
tion of the arrows shows that two atoms of oxygen, one taken from an atom of carbonic 
acid, and another from an atom of water, are set free by the plant, and dismissed into the 
air ; while the carbon and oxygen atoms, which remain of the carbonic acid, and the 
hydrogen from the water combine, as is shown by the arrows pointing downward to form 
the simple sugar atom. The formula of carbonic acid being COO, that of grape sugar is 
COH, an atom of hydrogen derived from the decomposition of water, being substituted 
for one of oxygen. This, however, is only to show in the simplest manner how grape 
sugar may originate; it does not consist of 1COH, but of 12 COH; that is, it contains 
twelve atoms of carbon, twelve of oxygen, and twelve of hydrogen. An atom of grape 
sugar would thus require for its production twelve atoms of carbonic acid to furnish its 
carbon and oxygen, and twelve of water to furnish its hydrogen ; these, by decomposition 
in the process of growth, yield twenty-four atoms or equivalents of pure oxygen, which is 
furnished by the plant to the atmosphere. 

197. In Plate VIII. I have represented the atom of grape sugar as being thus formed, 
that is, by the replacement of an atom of oxygen in carbonic acid, by hydrogen from 
water. But we may also suppose it to be produced by depriving the carbonic acid at 
once of all its oxygen, and replacing it by water, or the elements of water. In the repre- 
sentation of starch (Plate VIII.), I have changed the relative position of the oxygen 
and hydrogen atoms from OH to HO, which regards the elements as existing in the com- 
pound in the shape of water. We know that this group of substances is composed of 
carbon and the elements of water, but whether these elements are arranged as water is 
not determined. On that view these substances would be simple hydrates of carbon, 
charcoal, and water. Cane sugar, C 12 H lt O u , and starch, C 12 H 10 O 10 , contain an excess of 
carbon over the other constituents. They may be converted into grape sugar by the 
addition of one or two atoms of water, or may have been derived from it by the separation 
of one or two water atoms. 

198. The sugars differ in composition. The sugar of milk and the sugar of fruits 
(grape sugar), are C 12 H 12 12 , while cane sugar is C 12 H u O n , and gum has the same com- 
position. Starch and woody-fibre (cellulose) are also identical, their formula being 
C 10 H 10 O 10 . Starch and woody-fibre are therefore isomeric (157), as is also cane 
sugar and gum, their difference of properties being probably due to the arrangement of 
their molecules. 

199. Included in the oil and fat groups we observe four compounds ; glycerine with 
stearic, morgaric and oleic acids. These acids exist together in most fats and oils ; some 
of them are found in all. Fats and oils are believed to be composed after the manner of 
salts ; they consist of acids and a base. The common base is glycerine ; the acids which 
are in union with it are stearic, margaric, and oleic. Stearic acid with glycerine forms 
stearine, margaric acid with glycerine forms margarine, and oleic acid with glycerine 
yields oleine. Oleaginous bodies consist of stearine, margarine, and oleine, in all varieties 
of proportion. 

200. In forming soaps we but decompose the oil-salt, substituting potash, soda, 


or ammonia, for the natural organic base glycerine. (See Class Book, oils, fats, and 

201. The oils and fat are derived, like the vegetable acids and the neutral ternary 
compounds, from carbonic acid and water. They differ from them only in the extent to 
which the process has been carried. They are seen to contain a very large proportion of 
carbon and hydrogen, and. a very small quantity of oxygen. To form a simple atom of 
stearine (stearate of glycerine), forty-two atoms of water would require to be decomposed 
to furnish their hydrogen, and forty atoms of carbonic acid, thirty of which would have 
to be deprived of their entire amount of oxygen to furnish carbon. In producing a single 
atom of stearine, therefore, the plant sets free and surrenders to the air 112 atoms of pure 
oxygen gas. 

202. It will be noticed that the chemical difference between these groups of ternary 
compounds consists in the relative proportions of their constituents. In the organic acids 
we have the smallest or minimum quantity of hydrogen, and the largest or maximum pro- 
portion of oxygen ; in the sugar and starch group we have an increased proportion of 
hydrogen, and a diminished relative quantity of oxygen ; and in the fat and oil group, we 
observe a very large amount of carbon and hydrogen, with a minimum proportion of 
oxygen. The proportions in the organic acids are inverted in the fats and oils ; the neutral 
compounds, as they are intermediate in position, upon the chart also possess intermediate 
proportions of their constituents. 

203. Those who have referred to the Class-book, to learn the properties of the indi 
vidual elements of which we are speaking, will remember that carbon and hydrogen have 
each powerful attractions for oxygen, but hydrogen more than carbon. Ordinary fire or 
combustion is caused by the union of the oxygen of the air with the carbon and hydrogen 
of organized compounds. The products of burning are therefore oxygen combined with 
carbon and hydrogen ; that is, carbonic acid and water. Those substances only are com- 
bustible — that is, capable of being burned — which contain elements as carbon and hydro- 
gen, not associated with oxygen. Burning is thus an oxidizing process, and is the very 
reverse of what takes place in the plant. The carbon and hydrogen of carbonic acid and 
water having been burnt once, cannot be burnt again until they are separated. This the 
plant does : it imparts combustibility to carbon and hydrogen ; that is, it forms out of 
these two elements combustible compounds, by freeing them more or less completely from 
oxygen, and then uniting them together. 

204. Now as the combustibility, or power of burning and producing heat, which a 
substance possesses, depends upon the hydrogen and carbon which have been withdrawn 
from water and carbonic acid, and laid up in the compounds, it follows that the degree of 
combustibility, or the amount of heat which the substance is capable of giving out, will 
be exactly proportional to the quantity of hydrogen and carbon which have been sepa- 
rated from oxygen to produce it. An atom of hydrogen existing in water is incombusti- 
ble : withdrawn from water, it is combustible. An atom of carbon in carbonic acid is 
incapable of burning, because it can combine with no more oxygen. If it lose one atom 
of oxygen, it becomes combustible to a certain degree ; that is, it can resume the atom of 
oxygen : if the carbonic acid lose both atoms of oxygen, it becomes doubly combustible, 


because it is capable of uniting with a double quantity of oxygen. Hence the combusti- 
ble, or heat-giving powers of a compound, depend upon the completeness with which the 
hydrogen and carbon existing in it have been separated from oxygen. 

205. It will at once be seen, by reference to the diagram (Plate VIII.), that the 
vegetable acids are of low combustibility — possess but small heat-imparting power. They 
contain but very little hydrogen, and their carbon has been freed from less than half its 

206. The neutral ternary compounds stand higher in the scale of combustible power; 
the proportion of hydrogen is much greater, and that of oxygen is reduced. The fats and 
oils consist almost entirely of hydrogen and carbon, there being but the smallest propor- 
tion of oxygen, and their power of producing heat is correspondingly high. 

207. Now, when these different substances are burned, their combustive or calorific 
effects are shown to be in exact accordance with the relative proportions of their ingredi- 
ents. The vegetable acids are burned with difficulty, and yield but a small amount of 
heat. Starch, sugar, and pure woody-fibre, bum freer, and with augmented heating 
effects ; while the oils and fats — the pitches, rosins, bituminous coal — the whole hydro- 
carbon group — burn furiously, and with the evolution of large quantities of heat. 

208. But it is not as fuel that these substances are employed : they are universal and 
very large — nay, the chief ingredients of food ; they must subserve certain important pur- 
poses in the system, and we cannot doubt that their special properties are adapted to the 
accomplishment of these purposes. We certainly cannot think that their variations of 
chemical composition, and corresponding intensities of combustive power, are without 
physiological significance. 

209. These alimentary principles are taken into the system, are digested, and pass into 
the blood. At the same time oxygen is introduced into the lungs by respiration, and 
passes also into the blood. These compounds disappear, and, in the place of the oxygen 
introduced by inspiration, carbonic acid and water are thrown from the body by expira- 
tion. We breathe in pure oxygen, and breathe out oxygen in union with hydrogen and 
carbon ; and, at the same time, heat is generated within the body, by which its temperature 
in all healthy circumstances is maintained at a fixed point. We therefore conclude that 
animal heat is the result of combustion going on at a slow rate within the body ; and 
that the class of aliments we have been considering are designed to minister to this 
purpose — that is, to feed the physiological fire, to generate animal heat. When we con- 
sider that the body is maintained at the same temperature in winter and in summer, amid 
tropical burnings and polar frosts, it will be apparent that the amount of heat which the 
system is required to generate is liable to much fluctuation. Equally apparent, also, is 
that providential wisdom which has so modified the composition, and graduated the 
power of our heat-producing aliments, as to adapt them to all the exigencies of man upon 
the globe. 

210. The chemistry of animals is thus the reverse of that of plants. The latter pro- 
duce organized compounds, the former destroy them. Plants use carbonic acid and 
water for the production of organic compounds ; animals use organic compounds for the 
production of carbonic acid and water. This point will be considered more fully in a 
subsequent chapter (272). 



211. Tlie ternary compounds which we have regarded as designed simply for animal 
combustion and the maintenance of bodily heat, are not nutritious — that is, they are 
incapable of nourishing the body. In a proper sense, nutritive foods are those only which 
are capable of being converted into the structure or fabric of the system — of forming 
muscle, nerve, or some of the organized solid tissues of the body. Now the non-nitro- 
genized substances are totally incapable of this. The oil group may be laid up as fat, 
and sugar and starch may be converted into fat in the body ; but fat cannot form struc- 
ture, and it exists in the body as an unorganized mass, deposited within the cavities or 
sacs of cellular tissue. 

212. The composition of the ternary compounds deprives them of nutritive power. 
They cannot furnish to the fabric the materials that it demands : they are deficient in two 
essential ingredients of organic structures. These all contain nitrogen to a large extent ; 
it is the foundation element of muscles, nerves, and all tissue. Some parts of the fabric 
contain also sulphur as an indispensable element, and the ternary compounds can furnish 
neither. They are non-nitrogenized and non-sulphurized, and as the elements which they 
do contain are believed to be incapable of transmutation into nitrogen and sulphur, 
they are regarded as essentially innutritious. 

213. Animal nutrition is carried on by substances which have a vegetable origin — are 
formed in plants, and contain all the elements necessary to produce the various tissues in 
due proportion for this purpose. 

214. There is a compound formed by plants called vegetable albumen. It is a 
universal and quite abundant element of the various mixed foods we consume, and is 
exactly the same as the albumen found in blood and flesh, where it always exists. Iden- 
tical with albumen is the gluten of grain or vegetable fibre, which has precisely the same 
composition as the fibrin e or muscular portions of flesh. 

215. The composition of these compounds is very complex, and has been difficult of 
determination; if indeed it be now correctly known. They contain five constituents; 
carbon, oxygen, hydrogen, nitrogen, and sulphur, and a great number of atoms. So 
numerous are the atoms that it becomes impossible to represent all by diagrams, and I 
have hence in Plate IX. employed figures to express quantities. It will be seen that an 
atom of albumen or fibrine contains of carbon 216 atoms or equivalents, of hydrogen 
169, of oxygen 68, of nitrogen 23, and of sulphur 2. The old formula of Liebig, 
C 48 H 36 O u N 6 , though approximately correct, is not high enough to give the true propor- 
tion of sulphur, which has been since ascertained. ~No free phosphorus is present in these 
compounds as was formerly supposed. 

216. Peas and beans contain a principle which is identical in composition with curd 
or casein of milk, and is hence termed vegetable casein. Albumen of eggs, in its carbon, 
oxygen, and hydrogen, is identical with vegetable albumen and albumen of blood ; but it is 
richer in nitrogen, and contains one half more sulphur. Theine and caffeine are nitrogen- 
ized principles obtained, the former from tea and the latter from coffee, and which have 



Elements of Nutrition — their Source and Composition. 



■ SB 

and Sulphur- 
ic Acid are 
the source 
plants obtain 
the elements 
of the nitro- 
genized com- 

Composition of 

Vegetable and Animal I 

Albumen of Blood, 

of Flesh, 

of Vegetables. 
Fi brine of Flesh, 

of Vegetables. 

'288 s 228 


'216 ^169 



Albumen of Eggs, 

Fibrine of Blood, 

19 B 10 

[ ™216 ^169 

'298 a 228 



Choleic Acid, 

Cholic Acid, 

Uric Acid, 

'72 H 59 

[ "82 B 67 

'52 4 5 

'52 43 

'10 4 









— which exists in the fluid 
excretions of the body, 
and is converted in putre- 
faction into two atoms of 
carbonate of ammonia, by 
the addition of the ele- 
ments of two atoms of 








■ ■■ 

and sulphur- 
i z e d com- 
► pounds form- 
ed by plants, 
and consum- 
ed by animals 


These com- 
pounds exist 
in the hu- 
man body, 
and are deriv- 
ed from the 
principles o f 
food, repre- 
sented above 
bv a series 
of decomposi- 
tions occur- 
ring in the 

Water added when 
urea passes into 
carbonate of am- 


the same conrposition. They are feeble bases, and may represent a class of substances 
containing nitrogen, and known as vegetable alkalies. 

217. The nitrogenized bodies are obtained by plants from carbonic acid, water and 
ammonia, and their sulphur from the sulphates, plaster, tfec. Their mode of formation is 
not so simple as in the case of the non-nitrogenized compounds shown at Plate VIIL, 
and I shall not attempt to represent it. It is highly probable that the principle of coup- 
ling (124) comes largely into play in the formation of these compounds. 

218. The relations between these substances are very striking, and suggest changes 
which probably take place within the animal system. Thus casein the nitrogenized prin- 
ciple of milk, and from which all the albumen of young animals is derived, contains 
an excess of carbon, hydrogen, oxygen, and nitrogen, over albumen. In its conversion, 
therefore, into albumen in the body, that excess is separated, and when we compare the 
composition of these two compounds (Plate IX.), we find that an atom of casein will 
yield an atom of albumen, and with ten equivalents of oxygen, also an atom of chondrine, 
the organized principle of cartilage. Curd of milk, therefore, contains albumen for 
the blood and flesh of young animals, and with a little oxygen, chondrine also for the 

219. Gelatine is the nitrogenized principle of bones. Choleic and cJiolic acids are nitro- 
genized constituents of bile, the former containing also a large proportion of sulphur. 

Jlric acid and urea are constituents of the liquid animal excretions. 

220. Now, chondrine, gelatine, choleic, and cholic acids, uric acid and urea, are com- 
pounds formed in the animal body. It will be seen by the diagrams (Plate IX.), that 
they are all simpler in structure than the albuminous compounds of plants, of blood, and 
of flesh. They are all unquestionably derivatives of those more complex substances, and 
derived chiefly by processes of oxidation. We have already seen (209) that the animal 
is a machine of oxidation — the oxygen combining with hydrogen, and carbon of the ter- 
nary compounds, to maintain animal heat. 

221. The agency of oxygen has also evidently a large share in the transformation 
and gradual simplification of the nitrogenized substances, as seen in Plate IX. The more 
complex compounds may be at once split up into simpler ones, or more gradually changed, 
but in either case oxygen is regarded as the all-controlling agent of change. As animal 
heat is derived chiefly from the oxidation of the non-nitrogenized constituents of the blood, 
so motion, force, and animal power, are probably due directly to the oxidation of the nitro- 
genized tissues. 

222. The sulphur of the system is oxidized before escaping from it, and passes out in 
the form of sulphuric acid in combination with alkalies. The nitrogen is expelled from the 
body in the shape of urea, which is almost carbonic acid and ammonia ; it is changed in 
putrefaction to carbonate of ammonia by absorbing the elements of water, as is beauti- 
fully shown in Plate IX. One atom of urea with two of water give two of carbonate 
of ammonia. The highly complex nitrogenized principles are thus restored by the action 
of the animal organism to the simple binary compounds from which they were derived 
by plants. Here too we see the antagonizing action of plants and animals, the latter 
breaking down and destroying what the former build up and create. 



223. As all that live must die, so all organized compounds are destined in their nature 
to return to the inorganic state. Some of these substances go rapidly and some slowly, 
very slowly ; but we may look upon the whole organized world as moving or tending to 
dissolution. And although the forms which these compounds finally assume are few and 
simple, yet the intermediate products, which naturally arise, or may be formed by art, 
are varied and numberless. The organic compound, sugar, for example, may pass back- 
ward to its ultimate state of carbonic acid and water, by a great number of routes ; three 
of these are represented in Plate X. 

224. It has been stated that owing to their complexity of composition, organic com- 
pounds are of a transient nature ; and it may be added that of all organic substances the 
albuminous are the most perishable. The reason is obvious. An atom of albumen con- 
sists of five different elements and 482 equivalents or atoms. Affinities so numerous and 
complicated are liable to disturbance from very slight causes. Every one knows that 
milk, fresh meat, or wet flour, if left to themselves, in a short time putrefy. This is owing 
to their albuminous, glutinous and fibrinous elements, which speedily change. In these 
circumstances they run into spontaneous decomposition, and are hence termed putrefiable 
or putrescible compounds. 

225. The ternary compounds, which are less complex, and besides contain no nitrogen 
(see Class-book, — Nitrogen) have a more permanent composition. They do not tend to 
rapid and spontaneous decomposition. Nevertheless, when in the vicinity, or in contact 
with putrescent compounds, some of them are affected by the change, as it were con- 
tagiously, and pass into decomposition. Those compounds which do not spontaneously 
putrefy, and yet are transformed by the presence of putrescible substances, are termed 
fermentesdble, and the change is called fermentation. Sugar is a fermentescible 

226. If we add to a solution of sugar, at a temperature of from 40° to 86°, bread, 
milk, or flesh, in a condition of putrefaction, the change is imparted to the sugar, whose 
atoms are released from the saccharine affinity, and regroup themselves into the forms of 
carbonic acid and alcohol. Four atoms of carbonic acid (Plate X.) and two atoms of 
alcohol arise from a single atom of sugar. This is called the alcoholic or vinous fer- 
mentation. Fruit sugar (grape sugar), C 12 H 12 12 , is alone capable of this decomposition. 
Cane sugar, C 12 H n O u , before it becomes susceptible of this transformation, acquires an 
atom of water, and is thus changed to fruit sugar. Crystallized fruit sugar is C 12 H ]4 14 ; 
but the two atoms of water of crystallization separate and take no part in the change. 

227. When a solution of sugar is placed in contact with pressed curd or unsalted 
skim-milk cheese, which has previously been exposed to the atmosphere for some time, 
and the mixture is kept at a temperature of from 75° to 90°, a change takes place, the liquid 
soon becomes acidulous, and the sugar is converted into lactic acid. This is called the 
lactic acid fermentation. In this case no gas is formed as in the alcoholic fermentation, a 
single atom of sugar, C 12 H 12 ]2 , being separated into two atoms of lactic acid, 




{Grape Sugar.) 
(Milk Sugar.) 

Carbonic Acid. 

[ Fou r 

Products of the 
y vinous or alcohol- 
ic fermentation. 

I Alcohol. 


(Grape Sugar.) 
(Milk Sugar.) 

Lactic Acid. 

Products of the 
j> lactic fermenta- 

Lactic Acid. 


(Grape Sugar.) 
(Milk Sugar. 



k Carbonic Acid. 

■ ■ 

Free Hydrogen. 

Products of the 
f butyric fermenta- 

Butyric Acid. 


C H 6 O c , or C G H 5 5 + HO. This is the change that takes place in the souring of milk ; 
the milk sugar, Avhich has the same composition as grape sugar, being changed to lactic 
acid by the casein. 

228. Again, if the above mixture of curd and sugar be kept for some time at a 
temperature of from 90° to 105°, a new fermentation is established, and other compounds 
produced. The sugar is resolved into carbonic acid, C 2 (Plate X.), four atoms of free 
hydrogen, and an atom of butyric acid, C s H s 4 . This is hence called the butyric fer- 
mentation. The elements of the sugar in this case pass to butyric acid by the route of 
the lactic acid fermentation, and not directly as might be inferred from the diagram. 


229. We have seen that organized compounds may pass slowly from their condition 
of temporary constraint to the more j>ermanent and simpler forms which belong to the 
mineral condition. This change may also take place rapidly, where there is an abundant 
supply of oxygen, as in the open air, and it is there attended with the development of heat 
and light — combustion and illumination. 

230. Common combustion and illumination as we see them occur in the open air, 
are simply the result of the union of the hydrogen and carbon of the burning body with 
free atmospheric oxygen, producing carbonic acid and water. The organized comj)ound 
thus returns at a single step to the inorganic form — its organic structure is at once and 
entirely destroyed without the appearance of intermediate compounds forming successive 
stages of the process. 

231. We have seen that the beginning of organization consists in the separation 
of oxygen from carbon and hydrogen, and as the former of these two elements enters 
into all organized compounds, and the latter into very nearly all, this process is essential 
to the production of organic substances universally. As a consequence all organic sub- 
stances are combustible — that is, their carbon and hydrogen may return to the embrace 
of oxygen with the production of heat. The amount of heat generated is various ; the 
presence of oxygen and nitrogen in an organic compound hinders combustion. The 
vegetable acids and the albuminous compounds burn with difficulty, and produce the 
lowest calorific effects ; while those compounds in which they are entirely absent are most 

232. Of the four organic elements, therefore, carbon and hydrogen are those which 
impart to organic compounds the property of combustibility ; the oxygen and nitrogen 
present in them only regulating the intensity with which they burn. The compounds 
which we employ as sources of heat and light, are those which contain organized hydro- 
gen and carbon, sufficiently free from oxygen and nitrogen to be adapted to the various 
purposes for which we desire to use them. Woody-fibre is combustible, and used as a 
very general source of heat. If mixed or charged with substances richer in hydrogen 
and carbon, as rosin, pitch, &c, its combustive powers are greatly augmented. 

233. Carbon and hydrogen, when burnt separately, give rise each to a large amount 


of heat, but they exist in different forms, and burn in different ways. Carbon being 
always a solid, remains so during combustion. It becomes red and white hot, as we see 
in the combustion of charcoal or anthracite, but remains fixed and solid in the fire 
without altering its form, except as it gradually wastes away. Hydrogen on the contrary 
exists as a gas, and when burning, burns as a gas. If set free it tends to escape and 
diffuse into the air, and thus burns while in motion, giving rise to flame. Charcoal, 
unless containing moisture within its pores, which decomposes by heat, and yields hydro- 
gen, never burns with flame, while hydrogen can burn in no other way. Of course, then, 
where hydrogen and carbon are united, if burnt, they must produce flame. Wood, 
bituminous coal, the turpentines, resins, and oils, all burn with flame ; and the larger 
the quantity of hydrogen, the more furious the combustion, and the more voluminous 
the flame. 

234. The substances to be used for illumination, require to be very pure hydro- 
carbons. The compound which yields the largest amount of the clejirest light, when 
burned, is olefiant gas, which consists of nothing but carbon and hydrogen, and an 
equal number of atoms or equivalents of each. The camphenes, oils, tallows, <fcc, consist 
almost entirely of hydrogen and carbon, but these are in variable proportions, and- beside, 
they also contain some oxygen. Illuminating gas, the common substance which is burned 
in towns as a source of light, consists of olefiant gas mixed with other gaseous com- 
pounds ; and its value for illumination rises and falls, in proportion as this constituent 
increases or diminishes in quantity. 

235. Plate XL is an attempt to represent to the eye the chief conditions and 
changes which belong to the chemistry of illumination. I take for illustration the most 
perfect illuminating substance we have, olefiant gas — a pure hydro-carbon. It is 
represented as escaping from a gas-pipe in a jet, and is seen to be composed simply 
of hydrogen and carbon. For convenience, the atoms are shown of one fourth the size 
which has been employed in the former part of the work ; their combining proportions 
are, however, preserved. 

236. The diagram shows what occurs in burning a gas which has been previously 
manufactured for illuminating purposes. But essentially the same things take place 
when any other illuminating material is used, as liquid oil or solid tallow. They, also, 
consist mainly of hydrogen and carbon, and must be converted into gas before they can 
be burned. The oil of the lamp is raised by the wick, and converted into vapor before 
combustion can take place ; and the solid tallow of the candle is first melted into oil, and 
then raised and distilled into vapor in the same way. 

237. If any one will take the trouble to lower a piece of mica or fine wire gauze, or 
even a fragment of broken window-glass, over a gas-jet or candle-flame, it will be seen 
that the flame is not a solid mass of fire, but is rather a hollow shell of light, and is dark 
within. A ring of light is seen surrounding a dark interior space. This central space is 
filled witli the combustible principle to be consumed, the unburnt hydro-carbon gas. It 
is represented in Plate XL, as if the flame were split down from the top to the bottom, 
forming a vertical section, so that we are supposed to see what exists within. The 
unchanged gas is seen to fill the dark interior of the flame. 



Structure of Flame. 

The atoms are re- 
presented of one- 
fourth their for- 
mer size. The 
combining p r o- 
portions are pre- 
served. ■ 

The direc- i 
tion of the 
arrows indi- * 
catestheup- m 
ward cur- 
rents of 

1 Oxygen, 


Carbonic Acid, 


238. The gases which produce illumination — compounds of hydrogen, are lighter 
than the air. When set free, they therefore rise, or tend to escape upward. At the 
same time the heat of combustion rarefies the surrounding: air, which Leinir lighter. 
ascends also. Rising currents are therefore established, both within, and surrounding 
the flame, which carry it upwards, and thus occasion its conical or pointed figure. 

239. .The surrounding atmosphere in which combustion takes place, consists of free 
oxygen gas, which is therefore ready to combine with any substance for which it has an 
affinity. It is however, when pure, too powerful, and would burn with intense and 
ungovernable violence. Four times its bulk of nitrogen is hence mixed with it in the air, 
to restrain and temper it to the proper degree of activity. 

240. In the diagram, the free oxygen of the air is represented as rising toward the 
flame, in ascending currents in the direction of the arrows. 

241. As a consequence of this it will be seen that the oxygen will be in excess, that 
is, will accumulate in the largest quantity at the lowest point of the flame. But here it 
will be noticed, by directing attention to the burning of a candle or lamp, that the flame 
burns i>lue, and gives out but little light. 

242. The cause of this is, that in consequence of the abundance of oxygen the combus- 
tion is complete; the carbon and hydrogen being both consumed or burned at once. 

243. Now in the higher regions of the flame, which emit white light, this does not 
take place. The supply of oxygen is so regulated that the hydrogen and carbon may be 
burned in the order of their affinities. The affinity of hydrogen for oxygen is greater 
than that of carbon. Where the oxygen is presented in limited quantity to both, the 
hydrogen will seize upon it first, and will be burned first. This is what actually takes 
place in the illuminating flame. The nucleus of hydro-carbon vapor, which fills the in- 
terior of the flame, is decomposed at its outer surface where oxygen comes in contact with 
it. The hydrogen is oxidized first with the production of intense heat ; the carbon at the 
same instant being not burned, but set free. Those who have referred to the history of 
hydrogen in the Class-book, will recollect, that in combining with oxygen it gives rise to 
intense heat, but no light : its flame is hardly visible. The carbon is thus set free in 
exceedingly minute, solid particles, in the midst of a great heat. Those particles are 
therefore heated to whiteness, and thus give rise to vivid white light. The illumination 
comes from the solid, unburned particles of carbon, heated to brilliant whiteness by the 
burning hydrogen. 

244. The red-colored cone in the diagram, surrounding the central unburnt gas, is 
this region of partial combustion, and is the source of the light. The particles of carbon 
set free, for a moment float, or are pushed outward by those constantly liberated, until 
they find sufficient oxygen to burn them. This occurs in the exterior portion of the 
flame, which is represented in the diagram by a dark outer cone. Combustion is here 
completed by the oxidation of the carbon particles. 

245. Common combustion is thus an oxidation of hydrogen and carbon. Illumination 
results from their successive and regulated combustion ; and oxidized carbon and hydro- 
gen — that is, carbonic acid and water are the products formed. These are shown in the 
diagram (as they can at any time be proved by experiment) to be formed in the flame, 


and to escape in the upward current of heated air. The arrows pointing upward indicate 
their direction. 

246. Though water is the enemy of fire, yet it is itself the offspring of the fiercest and 
hottest combustion. All our common artificial lights result from the chemical production 
of water — the luminous effect proceeding from just that portion of the flame where water 
comes into existence. 

247. The flame thus undoes the work of the plant. It disorganizes vegetable pro- 
ducts ; and these simple changes which the diagram exhibits as going forward in a com- 
mon flame or burning candle, are the same that characterize combustion in the open air 
universally. All our fuels and illuminating materials in burning are oxidized to carbonic 
acid and water, and are thus fitted again to minister to vegetable nutrition — again to 
become sources of heat and li^ht. 


248. It is the pride of Astronomy to have shown that the harmony of our planetary 
system is preserved, and its stability guaranteed, by the eternal war of hostile forces. 
One, the centripetal, or centre-seeking force, if suffered to predominate, would bring all 
the planets to rest in a central mass ; another, the centrifugal, or centre-flying force, would 
whirl them away through space, in straight lines. But by the mutual checking and 
counteraction of these opposing powers, the planets are retained from age to age in 
their circling paths round the sun, and may thus continue to move harmoniously and for 

249. It is thus also with the course of life upon our globe. It is maintained by an 
omnipresent conflict of adverse forces, acting upon the chemical atoms of which living 
beings are composed. Constructive agencies, which originate life, and destructive agen- 
cies, which tend to death, are for ever in strife ; and vital existences perpetually perishing, 
but ever renewed, are the consequences. Like the solar system, living beings are the pro- 
duct of a balance between antagonizing energies — they spring from the harmonious 
adjustment of conflicting powers. 

250. Planto and animals are both endowed with vital or living properties ; they both 
grow, reproduce their kind, and perish. Yet the life of these two orders of beings is of a 
different nature, and depends upon different — nay, opposite conditions. The actions and 
changes in which vegetable life essentially consists, are exactly reversed in the case of 
animal life. 

251. Plants and animals can exist only in the air: this is equally indispensable to 
both. There are, indeed, numerous tribes belonging to both kingdoms which live in 
water ; but this is only because the elements of the atmosphere extend downward into 
the sea, and are found in all waters where life is present performing the same offices as in 
the aerial ocean above. The relation between the atmosphere and the life of each class is 
equally intimate and vital, and yet this atmosphere in the two instances performs diame- 
trically opposite offices. 


252. The common impression of the uninstructecl, who see the solid plant springing 
up from the solid earth, is, that the plant is formed entirely out of the soil, and has no 
more to do with the air than that it happens to be surrounded by it. Yet we might 
infer from the very structure of plants, that their connection with the air is in some way 
of the first importance. They are formed upon a plan which brings them into contact 
with the largest amount of air. Rising upwards to a greater or lesser height, the stems 
or trunks divide into branches, which are again divided into lesser branches, and those 
into minuter fibres or twigs, which expand out into innumerable flattened plates or 
leaves. Immense surface is thus secured. The branches and foot-stalks of the leaves 
being very elastic and easily bent, sway and tremble in every breeze, by which fresh 
air is continually supplied, and its surface contact with the leaf is greatly multiplied. 
Now all this wonderful contrivance and adaptation cannot be without some important 

253. We discover this purpose at once, when we compare what the air is made of 
with what the plant is made of. The plant and the air in which it grows are composed 
almost entirely of the same substances. Elementarily, they are almost identical. From 
one to five per cent, of the plant, its inorganic or mineral portion, its ash, comes from 
the soil ; the balance, the main bulk of the vegetable structure, 95 to 99 lbs. in a hun- 
dred of its weight, has the same constituents as the air. We get constant proof of this, 
in the burning which takes place in fireplaces and stoves ; the consuming wood, all but 
its ash, dissolves into gases, and rising upward, is thus actually converted into air. 

254. If the vegetable leaf is examined with a sufficiently powerful microscope, its 
surface is found to contain innumerable pores, openings, or mouths, through which a 
portion of the air enters to become food for the plant. Vegetation is thus nourished 
directly from the air; the air itself enters the leaves, and is changed into organized 
vegetable products. 

255. One of the constituents of the air, which may sometimes enter the plant through 
the leaves, exists also largely in the soil — this is water. It is the medium which dissolves 
the mineral or ash-elements, and carries them upward through the roots into the 
organism. Water is the leading substance of the green growing plant, and is also the 
medium for carrying on the operations which take place within its structure. To secure 
a constant upward current of it from the soil, it is perpetually evaporating away into the 
air from the extensive leaf-surface. The water which thus rises from the soil, contains also, 
dissolved, some of the gases which belong to the air, and which may have been washed 
down by rains, so that we cannot say that the plant actually takes in all its gaseous 
ingredients directly from the air through its leaves. Nevertheless, the process of gaseous 
absorption from the air constantly goes on, and the fact remains the same, that the plant 
and the atmosphere are nearly identical in their chemical elements. 

256. When a log of wood is charred in a pit, it is converted into a black mass of car- 
bon of the same form and size as the log was before charring. This carbon, as has been 
before stated, is the solidifying element of all organized fabrics. In the charring process, 
certain gases have been expelled into the ah', the solid carbon remaining. Now, that 
mass of charcoal, the chief solid constituent of the log, was derived by the growing tree 


from the air. It entered the leaves in the shape of a gas— carbonic acid gas, which is 
found every where diffused in small quantity through the air. About 1 -2000th the 
weight of the atmosphere is carbonic acid, and 6-22 of carbonic acid is carbon. 

257. The carbonic acid is decomposed in the plant, and furnishes this proportion of 
solid carbon. It is the office of the leaves and green parts of vegetation to perform this 
work, to effect the chemical separation of carbon from carbonic acid, that is, to deoxidize 
the carbon. Wherever a green plant exists, whether it be those which man cultivates as 
sources of food, or the venerable forest trees, or the wild weeds of the prairie, or the 
humble grass by the wayside, or the sea-weeds which grow in the ocean; this is its 
essential function — that in which vegetable life consists, to absorb carbonic acid gas, 
decompose it, use the carbon in forming organic vegetable compounds, and restore the 
oxygen back again to the air. 

258. The plant also decomposes water in the same way; employs its hydrogen in the 
manufacture of its peculiar products, and sets free the oxygen into the air. It also 
decomposes ammonia and nitric acid to get nitrogen, and sulphuric acid to get free sul- 
phur. These elements, carbon, hydrogen, oxygen, nitrogen, sulphur, and the ash-com- 
pounds from the soil, it makes use of to build up its own fabric — to grow. It is 
thus the prerogative of the plant to create organization ; so to decompose and recom- 
pound the elements of matter, that they shall acquire the quality of life. All vital 
structures in both worlds of organization, originate here in the green leaf. At this point 
disorganization and death cease, and life begins. 

259. How wonderful that the vegetable world thus springs into being from the bosom 
of the invisible atmosphere ! We can hardly grasp the fact as reality, that the beautiful 
forms which ornament the landscape, are really the children of the ethereal air ; that the 
fragrant and delicate flower has been really distilled from the pure and stainless medium 
which pervades it, or that the oak which has wrestled with winds and storms for hun- 
dreds of years, has nevertheless been nourished and developed by the very blasts which 
threatened it, and stands before us in its majesty, as consisting of but organized and 
embodied gases of the air. 

260. To fix distinctly in the mind the character of the changes wrought by growing 
vegetation upon the atmosphere, I have ventured again to resort to diagrams, which 
appeal to the eye. The effects produced upon the air by the vegetable world, are repre- 
sented in the left portion of Plate XII. The direction of the arrows shows carbonic 
acid and water, as it were, descending from the air, so as to enter the plant, at the same 
time that pure oxygen is set free, and rises, as it were, to take their place. It is not to 
be supposed, as the picture might seem to show, that the plant has any power of 
attracting downward from a distance the carbonic acid and water particles, or that those 
particles have any tendency to descend from the heights of the atmosphere to vegetable 
foliage. The inward and outward currents of gases take place at the surface of the 
leaf, and this great law of gaseous diffusion (see Class-Book) causes their dispersion and 
commingling. The diagram is simply designed to show what the plant receives and what 
it returns to the atmosphere, but this discloses to us at once the peculiar nature of vege- 
table life — the direction in which its forces are employed. 



Changes impressed by the Vegetable World upon the Atmosphere. Changes impressed by the Animal World upon the Atmosphere. 


261. Animals, it is well known, depend entirely upon vegetables for the substances which 
they use as food. An animal may consume flesh, but that, like all other flesh, comes 
ultimately from vegetation. The animal cannot, as the plant does, take carbonic acid, 
water, ammonia, and a few salts, and construct from them its own fabric. It has no such 
creative organizing power. It can only receive compounds that have been put together 
by the vital operations of vegetable growth, and in a certain manner transform them into 
its own substance. These compounds I have before described (182-221). 

262. Thus animals have the same ultimate origin as plants — they all alike derive the 
materials of which they consist from the air. They are composed of gases, condensed 
and solidified from the ethereal medium around us. Extraordinary as it may seem, not 
only the vegetation of the world — its forests of ancient trees, its multitudinous variety 
of herbs and shrubs, grasses and grains ; but also the entire animal kingdom — the thou- 
sand millions of human beings, and the numberless myriads of animated forms which 
compose the inferior races now inhabiting the earth — all, all must be regarded as derived 
from the subtile and viewless air, which has been temporarily imprisoned in organic forms. 
They preexisted in the realm of sunshine, and clouds of lightning and tempest. The 
atoms of which those living beings are now composed, and which minister to all the 
multiform vicissitudes of their existence, formerly wandered storm-swept and homeless in 
the ethereal regions above. By the action of the loftiest order of forces that play in the 
universe (275), these atoms have been arrested in their airy career, transmuted into solid 
and visible forms, and compose not only the book that you are now reading, but also the 
vital fabric of the person who reads it. 

263- But animals have a closer relation with the atmosphere than that the materials 
of which they are formed are indirectly derived from it. They depend upon it immediate- 
ly and constantly for the continuance of life. Their connection with it is as intimate and 
indissoluble as that of the plant, but in a different way, and for an opjuosite purpose. 
The animal, it is true, like the plant, is provided with an extensive absorbing surface 
to act upon the ah* ; but instead of being spread out externally like leaves, it ^s closely 
packed within the body in the shape of lung-membrane. There are some classes of 
animals, as insects and worms, whose breathing mechanism is placed upon the outer 
surface of their bodies ; but all the higher races have the pulmonary machinery arranged 
within. In these cases, the air is introduced by mechanical contrivances into the body, 
and exposed to the action of the absorbing membrane. Through this membrane the 
oxygen gas of the air passes inward, and enters the current of the blood, which carries it 
to all parts of the system. 

264. The compounds formed by the plant, and which the animal has used as food, are 
now to be decomposed — destroyed. A portion of them may have become parts 6f the 
living system ; the rest may exist dissolved in the blood. The oxygen which passed the 
membrane and entered the circulating blood, now seizes by its powerful affinity upon the 
carbon and hydrogen of these compounds, producing carbonic acid and water, which pass 
out through the same membrane, and are dismissed by expiration into the air. 

265. The animal thus undoes the work of the plant. It' withdraws from the air the 
substance which the plant gave to it, destroys the compounds which the plant created, 


and returns to the atmosphere those compounds which plants take from it. If the vege- 
table absorbs carbonic acid from the air, and returns pure oxygen, the animal, on the 
contrary, absorbs pure oxygen, and returns carbonic acid. If the plant decomposes 
water, which it may procure either from the air or from the soil, and pours into the 
atmosphere its separated oxygen, the animal extracts that oxygen, turns it again to water 
in its system, and expels it in the form of vapor into the air. 

26(3. This is shown upon the right side of the diagram (Plate XII.). Pure oxygen 
is represented by the direction of the arrows as passing from the atmosphere to the 
animal world, while carbonic acid and water are restored to the air in its stead ; thus 
exactly reversing the chemical changes which are seen to take place between vegetation 
and the air. The nature of the antagonism between these two orders of life thus becomes 
apparent at a glance. 

267. As vegetable growth involves largely the condensation of atmospheric gases, 
it is obvious that, if the animal is to undo the work of the plant, it must liberate the 
condensed gases, and set them free again in the air. This it is the fundamental office 
of animals to do. It unbinds, as it were, the packages of atoms which were bound up by 
the plant, returning them again to the gaseous form. If the essential changes of vegetable 
life involve the accumulation or aggregation of particles, construction, and necessary 
growth ; the essential changes of animal life, on the contrary, involve separation, disin- 
tegration, and perpetual self-destruction — the products of which are poured constantly 
into the air. At every breath a portion of the living fabric perishes, and escapes away 
into the region whence it was first obtained by the plant. 

268. In the nature of things, therefore, and by the innermost law of their being, all 
animals are doomed to a slow but constant dissolution. The act of breathing is an act of 
regulated and graduated destruction of the animal system : it is an incessant dying by 
particles, and in this consists the essence and peculiarity of animal life. 

269. It is beyond expression amazing to contemplate the powers and adaptations with 
which the atmosphere is endowed in relation to the origin and continuance of life upon 
the earth. Light, mobile, invisible, hardly tangible — of a tenuity pushed almost into the 
domain of spirit, we move about within it, yet unconscious of its presence. Nevertheless, 
it is here ; the most absolute and positive of realities ; mathematically certain in quantity, 
and every where invariable in composition. It is the fountain of life — the parent of all 
organized beings. From its serene and inscrutable depths come the silent and mysterious 
processions of life which crowd the earth. And not only does this atmosphere which 
envelopes our planet give birth to all the living hosts which inhabit it, but it contains 
also the agent which is to destroy them. Like the fabled god of antiquity — the symbol 
of time — it devours its own offspring. If the atmosphere lends the materials to beautify 
and adorn the earth with graceful and exquisite forms of vegetable life, and even to 
people it with intelligent existences, it is only for a transient duration. In a brief time 
she again demands her own. 

2 TO. The very act by which the plant brings into being bodies endowed with life, 
sets free also an agent which is appointed to destroy that life. This destructive agent of 
the air is oxygen gas. In the plan of nature, this substance occupies a position which 


brings it at once into intimate relationship with all species of living things. " To it is 
committed the duty to destroy all animal races, and transfer the parts of which their 
bodies are composed to plants. It begins to discharge this function the moment we 
begin to breathe, pervading each instant every part of our bodies, and bringing on 
interstitial death, and the continuous removal of particle after particle which it carries 
away. For there is an incessant change in the substance of all living structures : that 
which we are to-day differs from yesterday and to-morrow ; and this untiring agent is all 
the time at work assaulting and undermining, nor stopping its action with our dissolution, 
but going with us into the tomb, until it has restored every particle back to the air. 
Death is not, as the popular superstition says, a phantom skeleton ; nor, as the Asiatics 
think, a turbaned horseman, who pays his sudden and unwelcome visits. He is this 
invisible principle in the air which surrounds us, and which is the very breath we 

271. "When I consider the relations which oxygen gas maintains to the phenomena 
of this globe — constituting eight ninths of the waters of the sea, more than one third 
of the solid materials of the earth, and one fifth of the volume of the atmosphere ; — when 
I reflect on the office it discharges as the great destroying agent — that it causes the decay 
of animal and vegetable beings, and is the antagonist of life — that nearly all of the vio- 
lent, and even of the slow changes that take place, are due to it ; to use a daring 
metaphor, it is an embodiment of the destroying angel, who gives vigor to the conflagra- 
tion, and delights in the production of all kinds of violence and disasters." — Draper. 
It is even thus. And yet it must not be forgotten, that the life we live resides in this 
very destructive action of oxygen. 

272. It is then no more true that plants and animals are products of the air, than 
that in the due course of nature they will all be restored to it again. By active combus- 
tion and slow decay — by putrefactive decomposition, and by measured respiration, oxygen 
gas accomplishes its task of bringing back the organized world to the aeriform state. In 
that great receptacle to which we shall all return, there exists no traces of the brief 
distinctions which marked the transition of atoms through the life-period. Nature is 
an inexorable leveller. The breath of the outcast is mingled with the breath of the 
prince, and the bodies of both are finally dissolved and dispersed irrevocably through 
the restless air. And so of all that live. The crystal medium above, and through which 
the stars shine down upon us with their pure and blessed light, is the great sepulchre 
of past generations. It has received the disrupted and scattered elements of the dead 
that are gone, and is hourly gathering to itself the living of the present. 

273. It has been seen that the vegetable world impresses a universal and specific 
change upon the atmosphere. Taking into account the whole mass of the air, this change 
is undoubtedly slow. Nevertheless it is constant, and time alone is required to carry it to 
such a point, that if it were acting alone, it would entirely change and overturn the pre- 
sent constitution of the atmosphere. The quantity of carbonic acid would be so diminished, 
as to be incapable of supporting vegetable life. Any such imaginable result is provided 
against by the counteracting and antagonizing tendencies of animal life. The amount of 
carbonic acid, which might in time become deficient in the air, is kept up by animals 



which, generate this gas in large quantities ; or rather, this result is secured by the pre- 
sence of oxygen gas in the air, which by various conibustive operations, acting rapidly 
and slowly, destroys all organization, and perpetually carries back its constituents to the 
atmosphere. From this point of view, the organized world may be regarded as a grand 
automatic machine — a mechanism of self-continuance and self-adjustment. All excessive 
action is restrained by a system of checks and counterpoises, by which life and the ex- 
isting order of things are maintained. 

274. The diagram (Plate XII.), is suggestive of the essential hostility of the two or- 
ganized kingdoms of nature, of the direction in which their life-forces respectively tend, 
and of the harmonious balance which results. But it only indicates through a simple and 
striking fact the general law. Every thing cannot be thrown into pictorial form. It may 
aid us in seizing a prominent idea, but the details must be presented in other ways. The 
extent of the- antagonism of vegetable and animal life may be more clearly displayed as 
follows : 

Absokbs carbonic acid from the aie. 
Supplies oxygen gas to the atmosphere. 

Purifies the air. 

Decomposes carbonic acid, water, and 
ammoniacal salts. 

Produces the neutral nitrogenized com- 

Produces the non- nitrogenized com- 
vegetable acids. 

Endows mineral matter with the pro- 
perties OF LIFE. 

Imparts to chemical atoms the property 
of combustibility. 

Imparts to chemical atoms the power of 
nourishing the animal. 

Converts simple into complex compounds. 


is a mechanism of construction. 
Absorbs heat and electricity. 

Returns carbonic acid to the air. 
Withdraws oxygen gas from the atmos- 


Poisons the air. 

Produces carbonic acid, water, and ammo- 
niacal salts. 

Consumes the neutral nitrogenized com- 

Consumes the non - nitrogenized com- 

vegetable acids. 

Deprives organic matter of the pro- 
perties OF LIFE. 

Deprives chemical atoms of the pro- 
perty of combustibility. 

Imparts to chemical atoms the power of 
nourishing the vegetable. 

Converts complex into simple compounds. 

is an apparatus of oxidation. 

is a mechanism of reduction. 

Produces heat and electricity. 



275. We have seen in the foregoing passages, that there resides in the atmosphere 
which surrounds the earth, an omnipresent agent of destruction — a substance, which, by its 
essential nature, is the unrelenting, and ever-active foe of all organization. We call it oxy- 
gen gas. All forms and varieties of living things upon the earth, vegetable and animal, 
consist of elements in such a condition, that they are capable of being torn from their vital 
combinations by the affinities of this substance. Its disorganizing agency never ceases. 
Wherever there is a living being or an organized substance accessible to air, there this 
agent is always at work with greater or less activity, rending away particle by particle of 
the organic structure, until at last it is utterly broken down and destroyed. The active 
agency of the air is exerted upon the living world in a single direction for its destruction. 
It contains a force which, if left to itself, would speedily sweep from the globe all living 
existences, and to this destructive energy it opposes no counteracting or antagonizing 
power. It can dissever, but it cannot unite ; it can demolish, but it cannot build up ; it 
can disorganize, but it cannot construct ; it can cause to perish, but it cannot cause to 
grow. The oxygen of the air would soon change the green and beautiful and vocal 
earth to a dreary and silent sepulchre. Nor does the earth itself, the land or the sea any 
more than the atmosphere, contain a principle or power capable of checking or counter- 
acting these mighty destructive tendencies of the gases which enshroud the earth. The 
insatiate air devours the vital organism and the passive earth receives the scattered dust ; 
but neither can revivify or reorganize the disrupted elements. The earth carries within 
itself the causes of its own decay and dissolution, but not of its own renovation. It can 
destroy its living inhabitants, but it possesses within itself no power to replace them. 

276. Yet this destructive tendency of the air is checked and antagonized. The 
organism that oxygen consumed re-appears ; the atoms that it scattered are re-assembled ; 
the earth is green and beautiful, bursting with exuberant vitality, and teeming with 
animate beings. The stream of life flows on without arrestment or interruption. 

277. If then the earth is not the source and possessor of its own life-forces, whence 
come they ? That high power which originates organization, which gathers dead matter 
into living structures, and calls into existence all the beauties and glories of the earth, 
whence is it ? It is not of our world ; it is super-terrestrial ; it comes from the great cen- 
tral body of our planetary system, the stnsr. 

278. Beside the force of gravitation exerted by the sun, and which controls the 
earth in its orbital path, every one knows that we are connected with him through the 
medium of visible radiations or rays. The radiations which flow from the sun to the 
earth are capable of giving origin to several different kinds of effect. One of its effects 
is produced upon the animal eye, and is called light. In what manner light, or the 
luminous force acts upon the eye to generate vision, or cause the animal to see, we do not 
understand. We know many of the laws of light, but how the visual organ is finally 
affected in producing the sensation of vision, is not comprehended. 


279. If now we place a thermonieter, under suitable circumstances, in a visible ray of 
light, we shall observe that the temperature rises ; that is, the solar action has had the 
effect of forcing the particles of mercury in the thermometer to separate from each other 
so as to occupy a larger space ; the fluid metal therefore ascends in the thermometer 
tube, and we say the temperature rises. The sun's rays act in this manner not only upon 
mercury in the thermometer, but upon all objects on which they fall. They force apart 
or drive asunder the constituent atoms, so as to impart to objects a greater bulk. When 
the sun's rays act thus upon our bodies, they produce a feeling or sensation of warmth or 
heat. The a^ent which causes this effect is termed caloric. 

280. If the two gases, chlorine and hydrogen, be mingled together in the dark, they 
remain mixed or diffused through each other so long as they are retained in darkness. 
But if a ray of light be suffered to fall upon them, they combine together explosively, 
forming a new chemical compound. A force residing in the sunbeam thus produces the 
direct combination of chemical elements. If a piece of white paper be washed over with 
a solution of nitrate of silver, or any of the white salts of silver, and then exposed to the 
sun's rays, it will change color and become black. There is here a chemical decomposi- 
tion, which is brought about by the solar force associated with light. Many other sub- 
stances are also acted upon in a chemical way by the luminous beam. All daguerreotype 
pictures are products of the action of this force. The agent which brings about these re- 
sults is variously named. It has been called the actinic force, or actinism ; the tithonic 
force, and the chemical force, or the chemical ray. 

281. It has been conjectured that the forces which produce these various results — ■ 
lio-ht, heat, and chemical action — are essentially one : that the effects are but modifications 
or different manifestations of a single agent or power. According to the prevalent 
theory, heat and light are both but motion — vibratory or undulatory motions of the 
same ethereal medium — their differences consisting in the rate or velocity of the vibra- 
tions, light only appearing when they exceed from four to eight hundred billions in a 
second. However this may be, the fact remains that we have three classes of effects pro- 
duced by the solar radiations which are widely different, namely : luminous effects, which 
act upon the eye ; thermal or calorific effects, which expand all bodies ; and chemical 
effects, which play between different elementary substances, causing chemical changes. 

282. These three kinds of force are capable of being separated by analyzing, or as it 
were, splitting the sunbeam with a glass prism. If a ray of light be admitted through a 
small aperture into a dark room, and be suffered to fall upon a triangular prism of glass, 
it will not pass through it, and go forward in a straight direction across the room ; but 
it will be turned out of its pathway (refracted), and be thrown upon the opposite wall, 
not in the form in which it entered the room, as simple white light, but decomposed 
into an oblong image of the most brilliant colors, which is called the solar spectrum. 
This arrangement is exhibited in Plate XIII. The ray of light is represented as enter- 
ing the room, and passing into the interposed prism a b. But instead of emerging at 
exactly the opposite point, and passing on in the direction of the shaded line c d, it dis- 
appears, resolving itself into the colors which are roughly shown in the diagram. 

283. The colors produced under these circumstances are supposed to be the compo- 





nents or constituents of white light. Pure white lightconsists of all these colors ; and by 
passing the colored rays through another prism, they are again combined, and reproduce 
white light. When the image or spectrum is thus formed, the colors are not seen with a 
clear and sharp outline ; they blend and melt into each other, so that it is difficult to fix 
the line at which one ceases and another begins. Indeed, different eyes seem to receive 
different impressions ; for if several persons attempt to mark the exact spot where one 
color terminates and another commences, they will, in most cases, assign different points. 
The diagram exhibits what is known as the Newtonian spectrum, consisting of seven 
colors, in the order in which they are turned from their normal course — that is, in the 
order of their refrangibility. The red color is seen to be least bent from its natural path 
— the straight line — that is, it is least refracted. Orange is next ; it is more refracted ; — 
then yellow, green, blue, indigo, and lastly violet, which is the most refrangible color. 
By using prisms of different materials, the length of the space occupied by the respective 
colors of the spectrum is made to vary. 

284. If now, in this disappearance and destruction of the white ray, we search to know 
what has become of the luminous effect, we shall find that it is not equally distributed 
through the colored spaces. If we pass a piece of very fine print through the spectrum, 
we shall find that we can read it at a greater distance in the yellow space than in any of 
the other colors, showing that at this point there is most light. From the yellow space 
to either extremity of the spectrum the light declines. The curved line in the diagram, 
which extends from end to end of the colored spaces, from the extremity of the violet to 
the extremity of the red, represents by its curvature or height the intensity of the 
luminous effect. It is called the curve of luminous intensity, and its highest point corre- 
sponds with the yellow color, which is the maximum of luminous effect. 

285. Such is the influence of the prism upon the luminous principle of the solar beam. 
But what in this case becomes of the thermal or heat-producing principle which was 
associated with the light ? It enters the prism with the light ; how then is it disposed 
of ? Does it pass through it, and proceed in a straight course across the room, as indi- 
cated by the shaded line c d in the plate ; or is it dispersed over the spectrum in the 
same manner as the light? A thermometer placed at d, where the unrefracted ray 
would naturally fall, shows no rise of temperature. The calorific principle has therefore 
been diverted from its normal path — has been refracted. If now delicate thermometers 
are placed in the several colors of the luminous spectrum, it will be found that they are 
disturbed, and indicate an increase of temperature, but not in all the colors alike. A 
feeble heating effect will be shown in the violet color ; it will be increased in the indigo, 
and still more in the blue : in the green the mercury will rise higher, and in the yellow 
still higher. But is this point of the greatest luminous effect, also the point of utmost 
thermal effect % Do the luminous and calorific maxima coincide \ By no means ! The 
thermometer in the orange color indicates more heat than the yellow, and the red more 
than the orange. But what is most important, a thermometer removed quite out of the 
region of the visible red, where no light falls, shows a greater heating effect than at any 
point within the spectrum. The Curve of thermal intensity in the diagram exhibits the 
progressive increase of temperature from the violet to the red, and beyond this into the 


region of darkness, where the maximum of thermal influence occurs. We thus observe 
that the heat rays are refracted as well as those of color. They are dispersed over a 
region forming, we may suppose, an invisible calorific spectrum, which does not coincide 
in position with that produced by light, but laps over it, and extends beyond it, through 
the white space at e, in the direction of least refrangibility. The light-principle and the 
heat-principle, whatever they are, may be thus regarded as distinct, separable, and inde- 
pendent forces. 

286. But where is the third element of the sunbeam — the chemical principle or force? 
This is also turned by the prism from its straight course, and refracted as are the two 
others. If we wash over a sheet of white paper with a solution that may be acted 
on by this force, and notice where the chemical change or discoloration proceeds 
most promptly and rapidly, and is consequently strongest, we shall discover several 
curious facts. In the first place, the chemical action coincides in intensity with neither 
the luminous nor the calorific action. The maximum, or highest point of chemical effect, 
occurs in the violet region at the opposite extremity of the spectrum from that in which 
the thermal effect is produced. And in the next place, at the point of greatest luminous 
intensity (the yellow color) the chemical effect totally disappears — is completely neutral- 
ized. The curve of chemical intensity, as seen in the plate, exhibits this, and shows that 
there are two maxima of chemical influence. The greatest is in the highly refrangible 
violet region ; and there the chemical power extends beyond the extremest limit of light, 
in the direction of the prolonged white space at r. The chemical influence also extends 
beyond the red, at the other end of the colored series, as the curve shows. There appears 
then to be a chemical spectrum which does not correspond in position with either of the 
others, and a portion of which is separable and distinct from both. Thus the chemical 
constituent of the solar radiations is physically independent of the two other forces with 
which it is conjoined. The sunbeam produces three kinds of effects, so totally different 
in their nature as to be attributed to three distinct species of force, and which, moreover, 
appear actually and experimentally capable of separation. 

287. But besides these three forms of action exerted by the sun upon the earth, there 
is still a fourth kind, and it is the one with which we have mainly to do at this time. It 
is under the influence of the radiant force of the sun — either one of those which we have 
been considering, or another associated with them — that vegetable growth takes place. 
Plants require light to carry on their characteristic functions. They cannot flourish and 
form their peculiar organized productions out of unorganized matter in darkness. They 
demand the stimulus of light ; in other words, light is their motive power — the force 
which produces those fundamental and essential changes which appertain to and consti- 
tute vegetable life. The solar radiations supply the force which de-oxidizes carbon and 
hydrogen in the vegetable leaf. This is a chemical effect ; and we should at first certainly 
suppose that it is brought about by the chemical force which we have been contemplat- 
ing. But, singular as it may seem, this is not the fact. Dr. Draper has shown that the 
change wrought within the leaf, the decomposition of carbonic acid and water, and the 
setting free of oxygen, takes place with far the greatest activity in the yellow ray ; the 
point at which the chemical influence of which we have been speaking totally disappears. 


The effect is said to be due to light, as contradistinguished from the other agents of the 
sunbeam — that is, it takes place neither in the dark thermal space at one extreme of the 
spectrum, nor in the dark chemical region of the other : the changes only go on in the 
luminous field, and are most active where the light is most intense. 

288. Nevertheless, the action upon the leaf is in its nature so different from that upon 
the eye, that it seems hardly possible to ascribe them to the same cause. It is true, that the 
solar force which acts specifically upon the leaf, to bring about decomposing changes, has 
not yet been isolated or separated. But the work which it does is so essentially different 
from that of the other solar agents, that we seem justified in recognizing it as a fourth and 
distinct principle or power which resides in the sun's rays. That agent of the solar 
emanation, which conducts the decomposition, and controls the organizing processes that 
take place in vegetable structures, may perhaps at present be best distinguished as the 
de-oxidizing force, or the de-oxidizing ray. It is not to be supposed that this force acts 
with absolute independence. It is brought into play only under certain conditions, and 
one of these is the intensity of the conjoined calorific influence. 

289. I have been thus particular in describing the constitution of the sunbeam, be- 
cause we are now to contemplate it as the grand source of nearly every form of power 
which is manifested upon our globe. "Wherever we turn our attention all is motion, ac- 
tivity, demonstration of force. The atomsphere surges in storms and hurricanes ; the 
streams thunder over precipices, and set in motion the thousand-fold devices of mechani- 
cal industry ; steam urges on the dilatory ship, drives the swift train, or digs into the 
earth, or impels the factory ; electricity carries intelligence to the world's end with the 
speed of thought ; the vegetable world draws unorganized matter into its vital vortices, 
and fabricates the materials of life ; and the animal world is every where in motion, 
cleaving the air, dividing the waters, burrowing in the earth, traversing the land, and put- 
ting forth power in countless forms. Yet the placid and tranquil sunbeam is the grand 
source of all these manifestations of force — the great dynamical energy of the world. 
Those who have not had their attention especially drawn to the subject, are little aware 
of the tremendous agencies which slumber in the solar ray, or to what extent all kinds of 
terrestrial power are derived immediately from this source. 

290. In whatever respect we regard the solar emanation, it presents itself to us dynami- 
cally — as a spring of power. It is true that this is not so apparent in the case of the luminous 
principle which affects the eye. We cannot immediately demonstrate or measure the 
force which produces vision. But there can be no doubt that sight is the result of some- 
thing done ; the result of a power expended upon the optic organism ; the product of 
action and re-action between the luminous beam, and the atoms of nervous matter and 
arterial blood of the retina. All analogy compels us to this supposition. 

291. In the case of the chemical effect, as in the daguerreotype, the exercise of force is 
obvious. We here have a determinate movement of atoms, decomposition, power to over- 
come affinity. The solar impulse is sufficient for the transposition of chemical molecules 
and the destruction and production of compound substances. 

292. But the dynamic influence of solar radiation is more conspicuous in its thermal, 
or heat-producing effects. As the great luminary of the solar system, shoots down his 



calorific impulses, all objects upon which they fall increase in magnitude with an irresistible 
power. Material objects are larger, occupy more space at mid-day when exposed to the 
sun's direct influence, than at midnight when withdrawn from it. This change of the re- 
lations of atoms, although taking place with immense force, is yet so small in quantity, 
that when occurring in the solid substances around us we hardly notice it. But when the 
atoms of bodies are in such a condition as readily to yield to calorific agency, the effect 
at once strikes us with its vastness. The particles of air for example are easily put in 
motion ; the sun's heat therefore acting upon it, throws these particles into such active move- 
ment, that great masses of air are expanded, agitated and thrown into extensive motion. 
The unequal action of the sun's heat from various causes affects the atmosphere differently 
in different localities ; and the consequence is currents of air or winds in all directions. 
The gentle breeze, the driving gale, and the destructive tornado, are thus but manifesta- 
tions of force which come directly from the sun in the form of impulses of heat. The 
sails by which the ship is urged, on her commercial errand over the ocean, and the wind- 
mill which propels machinery, are alike driven by power which comes from the sun. 

293. The effect of the sun's heat falling upon the surface of oceans, seas, lakes, rivers 
and moist soils, is to change the liquid water to the state of vapor. This diffuses through 
the air, and is carried by its currents in all directions. Falling as rain upon the uneven 
land, it flows along in streams to the lower levels with sufficient power to be available for 
mechanical purposes. In this manner force which comes from the sun becomes converted 
into water power, and is used by man in a thousand ways, and for a thousand purposes. 

294. But the sunbeam is not only the source of wind and water power, it is also the 
great fountain of all steam and animal power. In a chemical point of view, steam and 
animal power are one thing, they both spring from the oxidation of carbon and hydrogen, 
which is supplied to the one in the shape of fuel, and to the other as food. For the pro- 
duction of a given mechanical effect, a steam-engine oxidizes a certain amount of carbon 
as coal, or of carbon and hydrogen in the shape of wood. And so with the animal ; for 
the performance of a certain amount of labor, a given quantity of organized carbon and 
hydrogen must be consumed — oxidized by the respiratory process. Combustion, or the 
chemical agency of oxygen gas is the immediate cause of both these manifestations of 
force. Oxygen is attracted to carbon, and hydrogen with a certain degree of energy, and 
in combining chemically with them it developes a corresponding degree of power which 
appears in the available form of heat. 

295. But it may be asked if steam power and animal power are thus due to the at- 
tractive energy of oxygen gas, how can we consider them as derived from the sun, or as- 
cribe them to the agency of his beams ? Let us see. The carbon and hydrogen which 
have united with oxygen are retained in its embrace with the same force which drew them 
into union ; for while in combination with their full proportion of oxygen, carbon and hy- 
drogen cannot be made to unite with it again. Water and carbonic acid though contain- 
ing the elements which produce combustion, cannot be burned, because their carbon and 
hydrogen are already saturated with oxygen, and consequently cannot attract more of it. 
The elements, before active, now come to rest ; there is no further source of power. 
When a certain quantity of oxygen burns a certain quantity of coal, both elements be- 


come locked up in the shape of carbonic acid, and they are locked together with the same 
force which they produced in burning. They have no power of self-releasment ; they 
have power to unite, but not to separate or escape from combination. It is therefore ob- 
vious that when all the accessible atoms of carbon and hydrogen in organized substances, 
have been seized upon by oxygen, oxidation must terminate, and there will be an end of 
all steam power, and animal power, all combustion and life. 

296. Steam power and animal power, combustion and life, thus depend upon a con- 
tinual supply of carbon and hydrogen in cm unoxidized state. But whence comes this 
supply \ One of two things must be true ; either there is somewhere in nature an ex- 
haustless fund of free oxygen and unoxidized hydrogen and carbon, and some place pro- 
vided for the reception and endless accumulation of the oxidized products ; or in the 
economy of the world some plan has been devised by which the same limited amount of 
materials may be used over and over again. The Almighty Contriver has resorted to the 
latter method ; the most wonderful economy of resources is characteristic of the ways of 
nature. ' The carbon and hydrogen which exist in union with oxygen are taken out of its 
grasp, separated, de-oxidized, put in a condition in which they can combine with it again. 
The carbon and hydrogen existing in oil or woody fibre have been burned under a steam- 
boiler, or in an animal body, and produce carbonic acid and water ; these now enter the 
vegetable organism, are carried to the green leaf, and there exposed to the action of the 
sunbeam, which decomposes them, restores their oxygen again to the air in a free and 
active condition, and again groups the hydrogen and carbon into the forms of oil and 
woody fibre. The oxygen thus set free and the organic compounds thus formed may now 
unite again and power will be again developed. Oxidation is thus the immediate cause 
of force, but it is the sunbeam which supplies the materials upon which oxygen can act. 
It is the sunbeam which impels the vegetable mechanism in the preparation of organized 
combustible compounds, and thus maintains the existing order of things. 

297. We may look on the present vegetation of the globe as a stock of de-oxidized 
carbon and hydrogen, prepared by the sun for the sustenance of animals, and for the use 
of man as a source of warmth and mechanical and chemical power. It is the sun which 
imparts to terrestrial matter combustible properties ; and for whatever purpose we em- 
ploy combustibility, the effect which it produces is ascribable to solar action. By means 
of a burning lens we can gather the heat rays of the sun into a focus and produce intense 
calorific effects. But all our more manageable forms of heat are due to the de-oxidizing 
ray. The chemist burns gas, oil, alcohol, or some other organized hydro-carbon in his labo- 
ratory, and thus brings about innumerable chemical changes and effects. The de-oxodizing 
force of the sun which grouped the organic molecules is transformed, or as it were trans- 
muted into heat in the burning lamp, and then again appears as a chemical result. The 
coal beds are deposits of de-oxidized carbon, the remains of an ancient vegetation ; they 
are reservoirs of force borrowed many ages since from the sun, and now available for 
the various uses of civilized man. 

298. It has been stated that electrical power generated in the galvanic battery, and 
employed through the telegraph for the transmission of intelligence, is due also to the 
sunbeam. The immediate cause of the electric current is the oxidation of the zinc, iron, 


or other metal of the battery, the oxygen being furnished by an acid or saline solution, 
which corrodes and dissolves the metal. But whence came the metallic iron, zinc or other 
oxidizable metal employed. It was reduced from the condition of ore, de-oxidized or de- 
sulphurized by the combustion of fuel in the smelting furnace. The recording instru- 
ment of the telegraph is moved by the magnet ; the magnet is formed and controlled by 
the electric current originating in the distant battery, and sent along the wires. The 
cause of the electric movement is the oxidation of the metal, and the metal was reduced 
from its ore, endowed with the capability of being oxidized by the combustion of carbon 
or hydrogen and carbon, and this, as has been shown, is the effect of solar excitation. 
Thus by a chain of effects we trace the motive power of the telegraph to the same celes- 
tial force which gives origin to organic life upon the earth. 

299. The amount of power which is expended in the de-oxidizing action of the solar 
rays is enormous. Whatever may be the force with which oxygen combines with 
carbon and hydrogen, and which retains them in union, it is evident that an equal or 
greater force must be exerted to separate them. Some of the metals possess a sufficiently 
strong attraction for oxygen to take it from hydrogen — that is, to decompose water at 
common temperatures ; and the electrical current is also capable of decomposing it, and 
setting free both its elementary gases. But it transcends the power of the chemist, by 
means of all the resources of his science, to take oxygen from carbonic acid at common 
temperatures — a thing which is done every day, in every green leaf, by the force of sun- 
light. By taking some substance which has a powerful affinity for oxygen, and aiding 
its action by an intense degree of heat, the oxygen may be forced into a new combination, 
and the carbon set free. But without the aid of any powerful de-oxidizing substance, or 
of any excessive heat, the plant decomposes carbonic acid, and sets the oxygen free. In 
doing this the sunbeam exerts a prodigious power. A bushel of coal combines in burning 
with about 200 pounds of oxygen; and if the combustion takes place under a steam- 
boiler, in the most favorable circumstances for the manifestation of mechanical effects, it 
will produce power enough to raise from 96 to 100 millions of pounds a foot high. The 
coal and oxygen take the form of carbonic acid, of which less than 300 pounds are pro- 
duced. In decomposing this carbonic acid the sunbeam exerts the same measure of force 
— sufficient to produce the mechanical result of raising 90 or 100 millions of pounds 
weight to the height of one foot. 

300. Dr. Geegoey remarks, that " the animal body may be regarded as a galvanic 
engine for the production of mechanical force : this force is derived from the food, and 
with the food has been derived from the solar rays. A working man, it has been cal- 
culated, produces in twenty-four hours an amount of heating, or thermal effect, equal to rais- 
ing near 14,000,000 of pounds to the height of one foot — heat being one form of mechani- 
cal effect. But from causes connected with the range of temperature, he can only produce, 
in the form of actual work done, about as much mechanical effect as would raise 3,600,000 
pounds to the height of one foot, and that in twenty-four hours. Even this is a prodigious 
amount of force ; and whether we regard it as derived from heat, electricity, or chemical 
action, it is ultimately derived from the luminous solar rays on which vegetation 


301. The same liigli authority remarks further: "That essential process by which 
the plant decomposes carbonic acid and water, liberating their oxygen, can only take 
place under the influence of luminous rays. Now if we consider that the chemical effects 
of light — light being motion — is a mechanical effect, and that the power necessary to de- 
compose carbonic acid and water is enormous, we see that the amount of mechanical effect 
produced in growing vegetables by the solar rays must be very great indeed. In fact it 
has been calculated that the mechanical force derived from the sun by the amount of 
wood growing in a year, on one square foot of surface, corresponds to that which would be 
required to raise a weight of 486,000 pounds to the height of one foot ; and this is only 
one eleventh of the whole effect of the sun's rays, of which only one fifth reaches the 
planet, and half of that is lost. Recent researches tend to show that all the mechanical 
effect (except in a few cases, such as tide-mills, volcanic action, and a few more) which is 
available to man, is derived from the solar rays, directly or indirectly. We have seen 
that a vast amount is expended in producing vegetables ; and it is obvious that the whole 
mechanical power of the animal body has been drawn mediately or immediately from that 
which has been stored up in plants." 

302. We thus see how it is, that the sunbeam antagonizes the destructive agency of 
oxygen gas. That agency can only take effect upon matter that the sunbeam has or- 
ganized. Creation must precede dissolution. Oxygen can destroy only that which the 
solar ray makes capable of being destroyed. We charge our systems at every breath 
with this substance, that by its disorganizing action it may give rise to the power we ex- 
pend. But we supply a continual resistance to this action in the form of food — the pro- 
duct of solar force, to renew the wasted parts of the fabric. As the destructive spirit of 
the air by decay, inspiration and active combustion, disintegrates organic structures and 
scatters their elementary atoms, the sun's rays exercise an equal power of an opposite 
kind ; they re-unite the dissevered molecules, and endow them again with the mysterious 
properties of life. 

303. By reference to Plate IV., it will be seen that the rock formations of the earth 
are composed of oxidized metals. About one half their weight consists of various metals, 
and the other half of oxygen gas combined with them. Now the sun exerts upon the 
earth a force of de-oxidation, a power which tends to separate oxygen from the substances 
with which affinity binds it. The earth is acted upon constantly by this force, in all parts 
of its orbit ; and that each portion of its surface may receive a share of the solar influ- 
ence the ponderous globe revolves rapidly upon its axis. Now the de-oxodizing force is 
capable of acting only upon the surface, and it cannot directly separate the oxygen from 
metals in stones and minerals. It is brought into play only in an appointed way and by 
appropriate mechanisms. The de-oxidizing agent acts mainly upon carbonic acid and 
water, producing hydro-carbon foods and fuels in the organism of the plant. At this point 
comes the agency of man. The de-oxodizing force stored up in vegetable compounds he 
expends to de-oxodize the metals which his multiform necessities may require. The 
laboring man becomes a director of forces which emanated from the central star of our 
planetary group; nay more, this is the origin of the very physical power which he 
himself exerts. 


304. It lias been stated that the two worlds of organization are condensed from the 
intangible gases with which our planet is enshrouded. If thus all living beings are de- 
rived from these fleeting airs, which are so rare and ethereal that they seem almost designed 
to connect the worlds of matter and spirit, it is fit that the forces which control such won- 
derful changes should have a celestial origin. If the grand office of pursuing to its final 
dissolution the entire organic world — of bringing its elements to the quiescent state — be 
committed to an agent which, when called up before us by the sorcery of the chemist, is 
but an invisible gas — a thing which no man has seen — it cannot surprise us that the force 
of antagonization by which all life and beauty and glory upon the earth are perpetually 
called into being, should be the divinest effluence of the stars — an activity which per- 
vades the universe. 

305. Astronomical science teaches us that the sun is but a star, and that the fixed stars 
are also suns, many of them being immensely larger than our own. The luminous principle 
which emanates from stars placed at the profoundest distances in space, affects the eye — is 
related to the optical mechanism of the animal, — its nervous tissue and circulating blood, 
in precisely the same manner as the light of our sun. Luminous impulses which expend 
themselves upon the retina in a few minutes after they have left the central orb of our 
system, affect the brain in exactly the same way as those which have been as many thou- 
sands of years travelling from the uttermost bounds of the telescopic universe. Further- 
more, the light of the stars exerts the same specific chemical effect, decomposes the salts 
of silver just as does solar light. Several of the fixed stars have been daguerreotyped ; 
that is, through spaces so vast that the imagination is tasked to conceive them, they 
have sent impulses which move chemical atoms, and control chemical changes. The 
chemistry of the staes is therefore an experimental reality. 

306. If, therefore, our sun, the great centre of vital dynamics, and fountain of life-im- 
pulsions, which has charge of the destiny of our planet, alike its atoms and its masses, be but 
a solitary star among the countless hosts of the celestial spheres ; if the earth be a scene 
of life, beauty and intelligence, only by virtue of its astronomical relations ; if the mes- 
senger of God, the solar beam, comes through the spacious amplitudes a hundred mil- 
lions of miles, to illuminate and vivify and people an otherwise desolate globe ; if the 
life-exciting forces traverse stellar distances and belong to astral systems, can we imagine 
even for a moment, that the phenomena of life are limited to our earth ? Can there be a 
question that organization is the product of a plan of agencies which comprehends the 
physical universe, and that the effect must be as universal as the cause ? 


I. Way in which the Blatter around us is com- 
posed. — 1. What changes do material objects undergo ? Give an illustration. 
2. "What is the first inquiry of Chemistry ? How does the chemist answer this 
question? "What is the meaning of the word analysis? "What is the limit of 
analysis? 3. "What forces are made use of in analysis? 4. What is the result 
of analyzing water ? "What is its limit? Of marble? 5. Is it possible or prob- 
able that our knowledge may be extended in this direction ? 6. In what man- 
ner do material substances and the sentences of a language resemble each other ? 
7. "What analogy is there between the number of letters in a language and the 
number of elements in nature ? 8. "What analogy is there between the fre- 
quency with which certain letters usually occur in words and certain elements 
in the most common compounds? 9. What is the synthesis of elements, and 
how does that resemble the formation of words ? 10. "What is said of the pro- 
perties and powers of these elements? 12. "What do the left columns in plates 
I. and II. represent? "What does each square indicate? Why is each element 
represented of a different color? Why have the special colors which are given 
to the elements in plates I. and II. been adopted ? 

II. Manner in which Chemical Substances com- 
bine. — 13. What do the right columns in plates I. and II. represent? How 
are the lines on these plates arranged, and what are they designed to express? 
How does chemical differ from other kinds of attraction ? What are the first 
fundamental conditions which make chemistry possible? 14. What is the first 
effect of atfinity ? What is said of mechanical combination? Example? 15. 
How does affinity affect the sulphur and iron mixture ? 16. By what are all 
chemical compounds characterized ? Give examples? IT. Upon what circum- 
stances does the loss of properties of elements, when they enter into combina- 
tion, depend? Examples? 18. What is the information got from analysis? 
What questions arise at this point? 19. When is the information we get from 
analysis restricted to the sample examined? What is it that here causes the 
difficulty? When may we generalize the information afforded by analysis? 
Upon what does the possibility of this depend? 21. What is the first law of 
affinity? How are chemical quantities expressed? Example? 22. What 
mode of representation becomes possible in consequence of the definite com- 
position of bodies? How are oxygen and hydrogen represented in plate I. 
What do the lines passing from them signify? What do the sizes of the squares 
represent? 23. What do the numbers connected with oxygen and hydrogen 
indicate ? What are they called? What relation have the areas of the squares 
to these numbers? What is the relation between the size of the square which 
represents hydrogen, and that of oxygen, chlorine and sulphur? 24. What is 
said of the importance of determinations by weight ? What kind of measure- 
ment do the squares express? 25. Are the combining numbers whole numbers 
or fractions which are given in the plates ? Why ? 26. What is shown by the 
fact that the carbon and hydrogen squares are maintained of the same size 
throughout the work? 27. What is eaid of the wonderful order of chemical 
combinations? 28. What is it that combining numbers measure? Give ex- 
amples? Explain the meaning of the term 'equivalent'? 29. What is meant 
by reciprocal proportions? Example? 30. In what does chemical decomposi- 
tion often consist? Example? 31. What is said of the scales of equivalent 
numbers? 32. What does the law of multiple proportions teach? 33. By 
what numbers may the quantities of oxygen, sulphur, and iron, found in com- 
pounds, be divided without a remainder? How are the equivalents of com- 
pound bodies ascertained ? Carbonic acid ? Lime? Marble? 34. What has been 
one result of the establishment of the principle of definite proportions? What 
are symbols? How do they represent compounds? What is the use of the 
figures joined to them? 35. What is the advantage of symbols? How is the 
composition of water expressed by the two methods of writing? 36. What is 
said about the order of arrangement of symbolic letters ? What is the relative 
position of hydrogen in plates I. and II.? Of oxygen ? Of the metals? Is there 
a reason for this ? What is it? Which side does the electro-positive element 
go ? 37. What does Liebig say of weighing in chemistry ? 38. When is it more 
convenient to measure than to weigh ? To what class of substances does bulk 
measurement apply? 40. How would we proceed to get the combining volumes 
of oxygen and phosphorus ? 41. How may the result be expressed? 42. How 
do we find the equivalent volume of hydrogen, and what is it ? 43. Nitrogen 
and chlorine, and what are theirs? 44. How does a knowledge of combining 
volumes become useful ? 45. What is the combining volume of hydrochloric 
acid gas? 46. What is the combining volume of steam ? 47. What of ammo- 
nia? 48. Is there any variation from the apparently simple law of combining 
volumes ? 

III. Theory of Atoms. — 50. What is the basis of the laws of com- 
bining proportions ? 51. What is said of the demands of the human mind ? 52. 
What is said of Newton's theory of gravitation ? 53. Can we suppose that the 
remarkable facts of combination exist without a cause? By whom has a cause 
in this case been assigned, and what is it ? 54. What does the word atom mean ? 
Can we discover atoms by observation ? 55-62. What examples are given of 
the degree of minuteness to which matter is divided? 63. What do these facts 
show? Ho these facts warrant us in supposing that matter is endlessly divisi- 
ble ? 64. What has the chemist reason for believing ? What objection is made 
to this ? What kind of indivisibility is it that the chemist affirms? 65. To 
what may chemical atoms be compared ? 66. What analogy is suggested to the 
atomic constitution of matter? In what sense may we consider the planets as 
indivisible units? 67. How is matter believed to be composed? In what 
manner are these atoms associated? 68. What does the atomic theory teach ? 
How are we to regard the atoms ? 69. By what are these propositions com- 
mended to us ? How do the laws of combination follow from the admission of 
atoms? Examples? 70. How do the diagrams upon the plates illustrate the 
atomic theory ? 71. What does Liebig remark concerning atoms? 72. Is the 
atomic theory in general use? 73. Is there any difference between 'atomic 
number ' and ' number of atoms ' ? What ? Examples ? 74. How is it common 
to use the term atom ? 75. What is supposed to be the form of atoms ? What 
figures seem associated with physical phenomena, and what with chemical or 
crystalline ? Why have square diagrams been adopted in this work to represent 
elements or atoms ? 

IV. Constitution of Salts— Theory of Salt-Radicals. 

— 76. What is the source of acids and bases? How are acids and alkalies 
usually known ? Are these tests satisfactory ? Why not? 77. What is their 
real test? What do they produce when united ? 78. Is it easy to decide what 
a salt is ? Is there agreement upon this point among chemists ? Is this sub- 
ject a difficult one to study ? How can we get assistance ? 79. To what salts 
is our attention first called in plate III. ? How are they represented? Have 
they long been supposed to be thus constituted ? What other acids combine 
in a similar manner? 80. If hydrochloric acid and soda are brought together 
what results ? How is common salt really produced ? In its analysis what do 
we get? Describe the double decomposition in plate III. ? 81. What follows 
if we adhere to the old idea of a salt ? What are halogens ? What is necessary 
in order to regard the haloid compounds as salts ? 82. What does the doctrine 
of salt-radicals propose to do? How does it begin ? S3. Where was oxygen 
found when first discovered? What was it supposed to be ? What was after- 
wards discovered? What are oxacids ? 84. What are hydracids? What are 
the elements which combine with hydrogen called ? How are the hydracids 
represented? 85. What are simple radicals? What are compound radicals? 
Example ? How does cyanogen behave like chlorine? 86. Upon what condi- 
tion are the acid properties of the oxacids developed? What is claimed by the 
advocates of the later or salt-radical theory ? What is objected to this ? What 
is the reply ? 87. From what facts is it inferred that hydrogen is the real acidi- 
fying principle? 88. How has water bei'n generally supposed to exist in the 
acids? 89. What is objected to this? 90. How does the new theory suppose 
the hydrogen to be combined ? How in the case of sulphuric acid ? Nitric 
acid? How does this bring all acids into one class ? 91. What do the advo- 
cates of the old view object concerning the isolation of compound radicals? 
What is replied? 92. Upon this view how do we convert aeidsinto salts? 93. 
What are Dr. Gregory's definitions of acids and salts? 94. What is illustrated 
by the diagrams of plate III. ? Why is hydrogen supposed to be a metal ? 95. 
What are the combinations of phosphoric acid with water? What is the result 
of substituting alkalies fortius combined water? 96. What does monobasic 
phosphoric acid form ? Example? The bibasic acid ? The tribasic acid ? 97. 
What is the basic phosphate of lime ? The neutral phosphate ? The superphos 
phate? 98. How is superphosphate of lime formed from bone dust? 99. How 
may the phosphates be represented by the salt-radical view ? 100. Do salts 
combine with each other ? When ? 

V. Chemistry of Geology. — 101. In what two forms are rockt 
found? 102. What is the aspect and origin of the unstratified rocks? Of the 
stratified? 103. What do the stratified rocks contain? Do unstratified rocks 
contain fossils? 104. What is said of the metamorphic rocks? Iu5. How is oui 
knowledge of the strata obtained? 106. What is said of the rate of action o. 
geological changes? 107. What geological changes are now taking place i 
What does Mr. Lyell remark? 108. What is the result of the continuous 



action of geological forces? What is a formation? 109. What follows from 
the order of succession? How is the order of time and of place illustrated? 
110. Can the complete series be any where observed ? In what manner may 
the formation be deficient? 111. How is the series completed:- 112. What 
has caused difficulty in arranging the rocks ? How have they been identified 
and arranged ? What is the geological service of fossils? How are the strata 
compared to the leaves of a book? 113. What does plate IY. represent? What 
appears at the right of the geological portion of the plate? At the surface? 
114. Upon what do geologists agree, and upon what disagree? 115. What 
might be supposed of the composition of the earth's crust? What is the fact? 
What is the geological meaning of the term 'rock 1 ? 116. How many minerals 
do we chiefly consider in geology? 117. What are they? 118. What is said 
of quartz? What rocks come from it ? 119. What is its chemical character ? 
120. What are the properties of talc? Serpentine? Hornblende? Augite ? Feld- 
spar? Mica? Carbonate of lime ? 121. What is said of the composition of these 
minerals? 122. What is said of granite ? Of what minerals is it composed? 
How do the proportions of these minerals affect it ? 123. What is said of 
granite as the parent of the rocks? 124. What is the position and composition 
of gneiss? 125. What is the composition of mica slate? Hornblende slate? 
Talcose slate ? Steatite ? 126. What is said of clay slate ? 12T. Of Serpentine ? 
12S. Of primary or crystalline limestone? 129. What is remarked of trap, 
greenstone, basalt, and trachyte ? 130. What is the composition of lava? 131. 
What is the position and composition of the Silurian system? 132. Of the 
Devonian system ? 133. Of the carboniferous system ? 134. The new-red 
sandstone? 135. The oolitic system ? Meaning of the word oolite ? 136. Tho 
cretaceous or chalk system ? 137. Of the tertiary formation ? 138. • The quar- 
ternary formation ? 139. How are these rocks all composed ? Are th.erc any 
additional minerals in considerable quantity ? What are they? 141. By what 
physical forces are the rooks altered ? 142. How does tho atmosphere act 
chemically to disintegrate rocks ? 143. How does water charged with carbonic 
acid act upon different rocks? How are the rocks changed to salts ? 144. Into 
what pairs are tho mineral elements of soils divided, plate II. ? 145. Is the de- 
composition complete? What relation has this circumstance to mechanical 
culture? 146. What is the meaning of fallow ? By what is it superseded? 147. 
What is said of the relation between the composition of rocks and that of soil ? 
Is there any difficulty in determining them ? 

VI. Structure of Organized Compounds.— 148. What is 
Organic Chemistry ? 149. What elements does it mainly consider? 150 What 
is said of carbon in organized compounds? 151. What is remarked of these 
grand results? 152. Are properties affected by proportions of the elements? 
153. Can the same substance exist in several conditions ? Example ? 154. What 
is this called ? 155. How may this affect the properties of compounds ? 157. 
W hat is stated of the grouping of atoms? 158. How does this doctrine agree 
with the old notions? 159, 160. What direct evidence have we of the fact of 
isomerism? 161. What illustration is offered? 169. When are compounds 
polymeric? 163. When metameric ? How does plate V. illustrate meta- 
merism ? 

VII. Theory of Compound Radicals.— 164. What does the 
doctrine of compound radicals assume? Example of simple radical? 165. 
What about ethyle, plate VI. ? 166. Formyle and acetyle ? 167. Have any or- 
ganic radicals been set free? Most of them? What is objected upon this 
ground ? What is replied ? 

VIII. Theory of Chemical Types. — 168. What is the origin 
'and necessity of this doctrine? 169. What is a chemical type? Give an illus- 
tration from the acids? 170. From the salts? 171. What illustrations of 
organic types are offered? 172. What examples are given upon plate VI, and 
how does the substitution take place? 173. Does the electro-chemical theory 
apply here ? 

IX. Pairing'. — 174. In what does pairing or conjugation of compounds 
consist? 175. What example is given, plate VI. ? 

X. Homologous Series oS Compounds. — 177. What is a 
homologous series? 178. What example is given upon plate VII. ? What is 
the common difference ? 179. What properties accompany this homology of 
composition? 180. How Jar has this scries been carried? How many were 
first known? 181. What is thought of this matter? 

XI. The TVon-iiitrogeniascd Alimentary Principles.— 

1S2. What kinds of compounds is it the office of the vegetable kingdom to 
make? 183. Are many organic compounds employed as food? What are 
they? 184. Can animals form their fond? 185. How are aliments divided, 
and by what circumstance? 186. Whence came the carbon, hydrogen, and 
nitrogen of organic compounds? 1S8. What is exhibited upon plate VIII. ? 
How are the ternary bodies divided? From whence are these compounds de- 
rived ? What do tho arrows pointing upward in the diagram signify ? Those 
pointing downward ? 189. How does the proportion of acid in carbonic acid 
compare with that in organic compounds? 190. How may organic compounds 
be regarded? 191. What is the composition and origin of oxalic acid? 192. 
What is here exhibited ? 193. What is the composition ot malic acid, and how 
is it formed ? What part does the water play ? 194. How may all the organic 
acids bo derived? How far may de-oxidation be carried to produco them? 

195. How do sugar, starch, and gum originate? What is their composition? 

196. How does grape sugar originate? How many atoms of carbonic acid and 
water would be needed to produce it? 197. How are the atoms represented in 
the starch, plate VIII. ? 198. What is the composition of the sugars? 199. 
What is the structure of the oil bodies ? 201. How do the oils differ in origin 
from the other groups ? 202. How are these groups related in composition ? 
203. How does combustibility depend upon chemical composition ? Why is 

not water combustible? 204. Upon what does the degree of combustibility of 
a compound depend? 205,206,207. What are hence the relative combustivo 
powers of the three groups? 208. Can we suppose these differences of compo- 
sition are of no physiological import ? 209. What must be their action and 
effects in the animal system ? 

XII. Nitrogenized and Sulphurized Aliments. — 211. 
Are the ternary compounds nutritious? 212. Why? 214. What is said of al- 
bumen and fibrine? 215. What is the composition of these substances? How 
are they represented in plate IX. ? 216. What principle does peas contain ? 
Composition of theine and caffeine? 217. Source of the nitrogenized princi- 
ples? 218. What is the relation of composition between casein and albumen ? 
219, 220. What is said of gelatine, chandrine, uric acid, &c. ? 221. By what 
force are these derived ? 222. What becomes of the sulphur? Of the nitro- 
gen ? Into what is urea resolved ? What is added ? 

XIII. Vinous, Lactic, and ESutyric Fermentation. — 

223. Do organic compounds in decomposition form many products ? 224. Why 
are the albuminous substances changeable? What are putriscible compounds? 
Fermentiscible ? 226. What are the conditions of the alcoholic fermentation ? 
227. Of the lactic acid ? 228. Of the butyric ? 

XIV. Chemistry of Comltustion and Illumination. — 

230. What causes combustion ? 231. What is the relation of organization to 
combustion? What influence have the nitrogen and oxygen of an organic 
compound? 232. The carbon and hydrogen? 233. How do they each burn ? 
234. What is the composition of illuminating materials? 235. What is exhib- 
ited in plate XI. ? 236. What occurs when solids and liquids are burned for 
light ? 237. How may the structure of flame be shown ? How is it exhibited 
in plate XI. ? 238. What causes the upward currents? The figure of the 
flame? 239. What is said of the air? 240. How is the oxygen represented in 
the diagram? 241,242. Why does the lower portion of the flame burn blue? 
243. Describe the changes in the burning flame? 244. What takes place in 
that portion of the flame represented by red color? 245. What do the arrows 
pointing upward show ? 246. What of water and combustion ? 

XV. Plants, Animals, and the Air.— 248, 249. In what re- 
spect do the solar system and life upon earth resemble each other? 250. Do 
plants and animals lead the same life ? 251. Are their relations to the air the 
same? 252. What is said of the connection of plants and tho air? 253. What 
relation of composition is there between plants and the air? 254. How is tho 
leaf constructed ? 255. What is said of water and the plant ? 256. What of tho 
source of the carbon? 257,258. What is the essential vegetable function? 
260. What is shown in the left portion of plate XII. ? 261. What is the imme- 
diate origin of all animal bodies ? 262. The ultimate origin ? The ultimate 
source of all living things? 263. What is the immediate relation of animals to 
the air? 264. What finally becomes of foods consumed? 265. What is shown 
upon the right side of plate XII.? 267. How are plants and animals related to 
atoms? 268. What is breathing? 269. What is said of the properties and 
offices of the air? 270. What is said of oxygen of the air? What does Dr. 
Draper remark ? 272. What is the destiny of the vegetable and animal worlds ? 
273. What of their constructing influences? 274. In whatrespects do the vege- 
table and animal antagonize each other? 

XVI. Chemistry of Light—Solar Dynamics. —275. What 
is recapitulated concerning oxygen'of the air? What is said of the relation of 
the earth to life? 276. Yet what is the fact? 278. How are we obviously 
connected with the sun ? Of the sense of vision ? 279. What other power has 
the sun's rays? 2S0. Describe its third effect? 281. What has been supposed 
concerning these foTces? 282. How can these forces be separated? What is 
shown in plate XIII. ? 283. Of what is white light composed? What order 
have the colors in the Newtonian spectrum ? 284. What becomes of the lumi- 
nous effect? What does the curved line which reaches from end to end of the 
colored spectrum show? 2S5. What becomes of the heat-producing principle ? 
What is the result of placing thermometers in the colors of the spectrum? Is 
there heat where is no light ? What is the position of the calorific spectrum, as 
shown by the curve of heating intensity ? 286. How does the prism affect the 
chemical force ? What is the position of the chemical spectrum? Where is 
its maximum? What does its curve show in plate XIII. ? 287. What is the 
fourth kind of action exerted by the sunbeam? Is it the'ehemical force which 
influences vegetation? Where is this force located in the spectrum? 28S. 
Why must we conclude that this is a fourth force? What is it last called? 
289. What is said of the sunbeam as a source of power ? 290. Of what is vision 
the probable result ? 291. Does the sun obviously exercise power in produc- 
ing chemical effects ? 292. How does heat affect all bodies ? How the air 
particularly ? How is the sun the cause of currents of air ? 2,93. How is the 
sun the source of water power? 294. To what are steam and animal power 
immediately due ? 295, 296. If steam and animal power are thus due to oxida- 
tion, how are they caused by the sun ? 297. How may we regard the earth's 
vegetation of the earth? Coal? 298. How is the power manifested in the 
telegraph traced to the sun ? 299. What is said of the amount of power put 
forth by the de-oxidating ray ? What is done every day in the leaf? What 
example of force is offered ? 300. How much is the mechanical effect of a 
working man ? What does Dr. Gregory state to be the source of this power? 
301. What amount of mechanical effect is exerted by the sun in vegetable 
growth upon a square foot? 302. How then is oxvgen concentrated? 303. 
What is the condition of the earth's materials, and how do the solar forces 
antagonize them ? What is the position and destiny of matter? 304. What is 
said of the character of the forces engaged? 305. What is the basis of tho 
chemistry of the stars? 306. What is the grand conclusion to which these 
views conduct us?